Control device and control program of walking assisting device

ABSTRACT

A control device and a control program of a walking assisting device, wherein a desired assist ratio, which is a desired value of the ratio of a force to be supplied by a walking assisting device in a total tread force of a user relative to the total tread forces is set, the shares of a lifting force to be applied to the user from a seating part which are to be borne by the leg links are determined from the desire assist ratio and the tread forces of the legs of the user measured on the basis of outputs of force sensors, and actuators of the leg links are controlled such that the determined shares of the lifting force are generated from the leg links. Thus, a force required for the user to support himself/herself by his/her legs on a floor can be reduced while reducing the number of parts to be attached to each leg of the user, and an assisting force for achieving such reductions can be properly shared between the leg links corresponding to the legs of the user.

This application is a divisional application from U.S. Ser. No.11/908,351, entitled CONTROL DEVICE AND CONTROL PROGRAM OF WALKINGASSISTING DEVICE, filed Sep. 11, 2007 (hereinafter, “ParentApplication”). The Parent Application is a national stage entry ofPCT/JP2006/310659, filed May 29, 2006, and claims priority to JP2005-158516, filed on May 31, 2005.

TECHNICAL FIELD

The present invention relates to a control device and a control programof a walking assisting device adapted to assist a user (human being)with his/her walking.

BACKGROUND ART

Hitherto, as this type of walking assisting device, there has beenknown, for example, the one disclosed in Japanese Patent Laid-Open No.H5-329186 (hereinafter referred to as Patent Document 1). According tothe walking assisting device (device for helping walking) described inPatent Document 1, supporting members are attached to the thigh, crus,and foot of each leg of the user. In the walking assisting device, thejoints that join these supporting members are driven by actuators toimpart a desired propulsion power to the user from the walking assistingdevice.

DISCLOSURE OF INVENTION

The walking assisting device described in the aforesaid Patent Document1 is capable of generating a desired propulsion power in a direction inwhich the user is moving thereby reducing the propulsion power requiredto be generated by the user himself/herself. However, as is obvious fromFIG. 15 in Patent Document 1, the weight of the user will have to besupported by the user himself/herself. This has led to unsatisfactorilyreduced load on the user. In addition, the one in Patent Document 1 doesnot have a technology for properly dividing a desired propulsion powerbetween the legs of the walking assisting device. Hence, there has beena danger in that a force that does not match a motion of each leg of theuser acts on each leg of the user. Further, according to the one inPatent Document 1, the supporting members of the walking assistingdevice are attached to the thigh, the crus, and the foot, respectively,of each leg of the user, and forces are applied from the supportingmembers to the thigh, the crus, and the foot of each leg. This has beenapt to make the user uncomfortable.

The present invention has been made with a view of the aforesaidbackground, and it is an object thereof to provide a control device anda control program of a walking assisting device that make it possible toreduce a force with which a user himself/herself has to support his/herlegs on a floor and to properly divide an assisting force for reducingthe aforesaid force by a leg link associated with each leg of the userwhile at the same time reducing the number of parts to be attached toeach leg of the user.

To fulfill the aforesaid object, according to a first invention, thereis provided a control device of a walking assisting device provided witha seating parting part that receives from above a part of the weight ofa user sitting thereon, a pair of right and left thigh frames joinedrespectively to the seating parting part through the intermediary offirst joints, a pair of right and left crus frames joined respectivelyto the thigh frames through the intermediary of second joints, a pair ofright and left foot-worn assemblies that are respectively joined to thecrus frames through the intermediary of third joints and respectivelyattached to the feet of the right and left legs of the user, and come incontact with the ground when the legs of the user become standing legs,an actuator for the left for driving the second joint among joints of aleft leg link composed of the first joint, the thigh frame, the secondjoint, the crus frame, the third joint, and the foot-worn assembly onthe left side, and an actuator for the right for driving the secondjoint among joints of a right leg link composed of the first joint, thethigh frame, the second joint, the crus frame, the third joint, and thefoot-worn assembly on the right side, the control device including:

a treading force measuring means for measuring the treading force ofeach leg of the user on the basis of a force detection value indicatedby an output of a first force sensor provided in each of the foot-wornassemblies;

a desired assist ratio setting means for setting a desired assist ratio,which is a desired value of a ratio of a force to be supplied by thewalking assisting device in a total treading force, which is the totalsum of the treading forces of the legs of the user, relative to thetotal treading force;

a desired lifting share determining means for determining a desiredlifting share which is a desired value of a share of the left leg linkand a desired lifting share which is a desired value of a share of theright leg link in an upward lifting force to be applied to the user fromthe seating parting part by multiplying a treading force of each leg ofthe user, which has been measured by the treading force measuring means,by the desired assist ratio; and

an actuator controlling means for controlling an actuator for the leftsuch that the lifting force actually imparted to the seating partingpart from the left leg link becomes a desired lifting share of the leftleg link determined by the desired lifting share determining means andalso for controlling an actuator for the right such that the liftingforce actually imparted to the seating part from the right leg linkbecomes a desired lifting share of the right leg link determined by thedesired lifting share determining means.

According to the first invention described above, only each of thefoot-worn assemblies of the walking assisting device is attached to thefoot of each leg. Moreover, a user has only to sit on the seating partso that a part of his/her weight is rested thereon.

Further, according to the first invention, the treading force of eachleg of the user measured by the treading force measuring means ismultiplied by a desired assist ratio set by the desired assist ratiosetting means thereby to determine a desired lifting share of the leftleg link and a desired lifting share of the right leg link in an upwardlifting force to be applied to the user from the seating part. In otherwords, the aforesaid measured treading force of the left leg of the useris multiplied by a desired assist ratio to determine a desired liftingshare of the left leg link and the aforesaid measured treading force ofthe right leg of the user is multiplied by a desired assist ratio todetermine a desired lifting share of the right leg link. Incidentally,the total sum of the desired lifting share of the left leg link and thedesired lifting share of the right leg link corresponds to the desiredvalue of the total lifting force applied to the user from the seatingpart, and this will be substantially equal to a force obtained bymultiplying a total treading force of the user by the aforesaid desiredassist ratio.

In this case, a treading force of the right leg and a treading force ofthe left leg of the user measured by the treading force measuring meansreflect an intention of a user on how to support his/her weight by eachleg on a floor. For instance, if the treading force of the left leg islarger than the treading force of the right leg, then it means that theuser intends to support his/her weight mainly with his/her right leg.Thus, according to the first invention, the desired lifting share ofeach leg link is determined by multiplying the treading force of eachleg of the user measured by the treading force measuring means by theaforesaid desired assist ratio. This makes it possible to distribute adesired value of a total lifting force to be applied to the user fromthe seating part (the total sum of the desired lifting shares of the leglinks) to the leg links such that it matches a motion state of each legdesired by the user.

Furthermore, according to the first invention, the actuator for the leftis controlled such that the lifting force actually imparted to theseating part from the left leg link becomes the desired lifting share ofthe left leg link determined as described above, and the actuator forthe right is controlled such that the lifting force actually imparted tothe seating part from the right leg link becomes the desired liftingshare of the right leg link determined as described above. Thus, alifting force corresponding to a force obtained by multiplying the totaltreading force of the user by the desired assist ratio can be applied tothe user from the seating part while dividing the lifting force betweenthe right and left leg links so as to fit the motional state of each legdesired by the user. As a result, a load on each leg of the user can beeffectively reduced.

Hence, according to the first invention, it is possible to decrease theforce required for a user to support himself/herself with his/her leg orlegs on a floor, while using fewer members to be attached to the legs ofthe user. Moreover, an assisting force (lifting force) for reducing theaforesaid force can be properly shared between the leg links associatedwith the individual legs of the user.

According to a second invention of the present application, there isprovided a control device of a walking assisting device equipped with aseating part that receives a part of the weight of a user sittingthereon from above, a pair of right and left thigh frames respectivelyjoined to the seating part through the intermediary of first joints, apair of right and left crus frames respectively joined to the thighframes through the intermediary of second joints, a pair of right andleft foot-worn assemblies that are respectively joined to the crusframes through the intermediary of third joints and respectivelyattached to the feet of the right and left legs of the user, and come incontact with the ground when the legs of the user become standing legs,an actuator for the left for driving a second joint among joints of aleft leg link composed of the first joint, the thigh frame, the secondjoint, the crus frame, the third joint, and the foot-worn assembly onthe left side, and an actuator for the right for driving a second jointamong joints of a right leg link composed of the first joint, the thighframe, the second joint, the crus frame, the third joint, and thefoot-worn assembly on the right side, the control device including:

a treading force measuring means for measuring the treading force ofeach leg of the user on the basis of a force detection value indicatedby an output of the first force sensor provided in each of the foot-wornassemblies;

a second force sensor provided between the bottom end of the crus frameand the third joint of each leg link or between the third joint and thefoot-worn assembly of each leg link;

a force-to-be-controlled measuring means for measuring, as aforce-to-be-controlled, a force actually transmitted from the floor tothe crus frame of each leg link on the basis of a force detection valueindicated by an output of the second force sensor;

a desired assist ratio setting means for setting a desired assist ratio,which is a desired value of a ratio of a force to be supplied by thewalking assisting device in a total treading force, which is the totalsum of the treading forces of the legs of the user, relative to thetotal treading force;

a desired lifting share determining means for determining a desiredlifting share which is the desired value of a share of a left leg linkand a desired lifting share which is the desired value of a share of theright leg link in an upward lifting force to be applied to the user fromthe seating part by multiplying a treading force of each leg of theuser, which has been measured by the treading force measuring means, bythe desired assist ratio;

a distributing means for distributing a supporting force required tosupport, on a floor, the weight obtained by subtracting the total weightof the portions below the second force sensors of the walking assistingdevice from the total weight of the walking assisting device, or asupporting force required to support the total weight of the walkingassisting device on the floor to the leg links on the basis of a ratiobetween a treading force of the left leg and a treading force of theright leg of the user, which have been measured by the treading forcemeasuring means, thereby determining the share of the left leg link andthe share of the right leg link of the supporting force as a desireddevice supporting force share of each leg link;

a force-to-be-controlled desired value determining means for determiningthe total sum of a desired lifting share of the left leg link and adesired device supporting force share of the left leg link as a desiredvalue of the force-to-be-controlled of the left leg link and also fordetermining the total sum of a desired lifting share of the right leglink and a desired device supporting force share of the right leg linkas a desired value of the force-to-be-controlled of the right leg link;and

an actuator controlling means for controlling the actuator for the lefton the basis of the force-to-be-controlled of the left leg link and thedesired value of the force-to-be-controlled of the left leg link suchthat the difference between the force-to-be-controlled and the desiredvalue of the left leg link approximates zero and for controlling theactuator for the right on the basis of the force-to-be-controlled of theright leg link and the desired value of the force-to-be-controlled ofthe right leg link such that the difference between theforce-to-be-controlled and the desired value of the right leg linkapproximates zero.

According to the second invention, only the foot-worn assembly of thewalking assisting device is attached to the foot of each leg of a user,as with the first invention. Moreover, the user has only to sit on theseating part so that a part of his/her weight is rested thereon.

Furthermore, according to the second invention, as with the firstinvention, the treading force of each leg of the user measured by thetreading force measuring means is multiplied by a desired assist ratioset by the desired assist ratio setting means thereby to determine adesired lifting share of the left leg link and a desired lifting shareof the right leg link of an upward lifting force to be applied to theuser from the seating part.

Meanwhile, according to the second invention, further, a supportingforce, which is required to support, on a floor, the weight obtained bysubtracting the total weight of the portions below the second forcesensors of the walking assisting device from the total weight of thewalking assisting device (the weight will be hereinafter referred to as“weight X” in the present column) or a supporting force required tosupport, on the floor, the total weight of the walking assisting deviceis distributed to the aforesaid leg links on the basis of a ratiobetween a treading force of the left leg and a treading force of theright leg of the user measured by the treading force measuring means,thereby determining the share of the left leg link and the share of theright leg link in a desired value of the supporting force as a desireddevice supporting force share of each leg link. In other words, thedesired device supporting force share of each leg link is determined bydistributing, to each leg link, the aforesaid supporting force requiredto support, on a floor, the weight X or the total weight of theaforesaid walking assisting device (this means a force that balances outthe gravity corresponding to the weight X or the total weight of thewalking assisting device) on the basis of (in conformity with) the ratiobetween a treading force of the right leg and a treading force of theleft leg that reflects a motion of each leg desired by a user. Morespecifically, for example, a desired device supporting force share ofthe right leg link may be determined such that the ratio of a desireddevice supporting force share of the right leg link to the desired valueof the supporting force equals the ratio of a right treading force tothe total sum of the treading force of the right leg and the treadingforce of the left leg of the user. Similarly, a desired devicesupporting force share of the left leg link may be determined such thatthe ratio of a desired device supporting force share of the left leglink to the desired value of the supporting force equals the ratio of aleft treading force to the total sum of the treading force of the rightleg and the treading force of the left leg of the user. Supplementally,in general, the weight X and the total weight of the walking assistingdevice are substantially equal.

Further, according to the second invention, the total sum of the desiredlifting share of the left leg link determined by the aforesaid desiredlifting share determining means and the desired device supporting forceshare of the left leg link determined by the aforesaid distributingmeans is determined as a desired value of the aforesaidforce-to-be-controlled of the left leg link, and the total sum of thedesired lifting share of the right leg link determined by the aforesaiddesired lifting share determining means and the desired devicesupporting force share of the right leg link determined by the aforesaiddistributing means is determined as a desired value of the aforesaidforce-to-be-controlled of the right leg link.

Thus, a desired value of a force-to-be-controlled of each leg link isdetermined to match a ratio between a treading force of the right legand a treading force of the left leg that reflects a motion of each legdesired by the user. In this case, a desired value of aforce-to-be-controlled of each leg link indicates the sum of a desiredlifting share of the leg link and a desired device supporting forceshare, so that the total sum of the desired values of theforces-to-be-controlled of the two leg links corresponds to the totalsum of a lifting force to be applied to a user from the seating part anda supporting force for supporting the weight X or the total weight ofthe walking assisting device.

Further, according to the second invention, the actuator for the left iscontrolled on the basis of a force-to-be-controlled of the left leg linkmeasured by the force-to-be-controlled measuring means and a desiredvalue of a force-to-be-controlled of the left leg link determined by theforce-to-be-controlled desired value determining means such that thedifference between the force-to-be-controlled and the desired value ofthe left leg link approximates zero, and the actuator for the right iscontrolled on the basis of a force-to-be-controlled of the right leglink measured by the force-to-be-controlled measuring means and adesired value of a force-to-be-controlled of the right leg linkdetermined by the force-to-be-controlled desired value determining meanssuch that the difference between the force-to-be-controlled and thedesired value of the right leg link approximates zero.

Thus, an actual force-to-be-controlled of each leg link (thiscorresponds to an actual share of each leg link relative to a totalsupporting force for supporting a load actually imparted to the seatingpart from a user (a force that balances out an upward lifting forceactually acting on the user from the seating part) and the gravity thatcorresponds to the aforesaid weight X or the total weight of the walkingassisting device) can be securely controlled to a desired value.Further, at this time, the actual lifting force acting on the user fromthe seating part can be controlled to a lifting force that correspondsto a force obtained by multiplying a total treading force of the user bythe aforesaid desired assist ratio.

Thus, the second invention makes it possible to properly apply a liftingforce to the user from the seating part by distributing a lifting forcecorresponding to a force, which is obtained by multiplying the totaltreading force of the user by a desired assist ratio, to the right andleft leg links so as to match a motion state of each leg desired by auser, while considering the weight of the walking assisting device. As aresult, a load on each leg of the user can be further effectivelyreduced.

Thus, according to the second invention, the force required for a userto support himself/herself with his/her leg or legs on a floor can bereduced, while using fewer members to be attached to each leg of theuser, and an assisting force (lifting force) for achieving such areduction can be properly shared between the leg links associated withthe individual legs of the user.

Preferably, in the first invention and the second invention describedabove, the foot-worn assembly of each leg link is equipped with anannular member for inserting a foot of the user, to which the foot-wornassembly is to be attached, from the toe end thereof, and joined to thethird joint of the leg link through the intermediary of the annularmember (a third invention).

According to the third invention, the major portion of a load impartedfrom a user to the seating part and the total weight of the walkingassisting device can be applied to a floor through the intermediary ofthe annular members (more accurately, through the intermediary of theannular member of the foot-worn assembly attached to the foot of the legthat becomes a standing leg) without causing it to act on the user. Thisenables the user to move each leg, hardly feeling the weight of thewalking assisting device.

In the first to the third inventions, the first force sensor of each ofthe foot-worn assemblies is composed of one or more force sensorsprovided in each foot-worn assembly such that, when, for example, eachleg of the user becomes a standing leg, they are positioned between atleast either the location of the metatarsophalangeal joint or thelocation of the heel of the foot on the bottom surface of the foot ofthe standing leg and a floor. Further, in this case, the treading forcemeasuring means is preferably a means that takes the total sum of theforce detection values indicated by outputs of the force sensorsconstituting the first force sensor of each foot-worn assembly as theforce detection value of the first force sensor and measures thetreading force of a leg of the user that has the foot-worn assemblyattached thereto on the basis of the force detection value of the totalsum (a fourth invention).

With this arrangement, the treading force of each leg can be properlymeasured. Especially when force sensors are provided at both thelocation of the metatarsophalangeal joint and the location of the heelof the foot on the bottom surface of the foot of the user (moregenerally, when a plurality of force sensors including the two forcesensors are provided), the treading force of each leg can be properlymeasured regardless of the posture of each foot of the user relative toa floor.

In the fourth invention, a force sensor may alternatively be providedonly at either the location of the metatarsophalangeal joint or thelocation of the heel. In this case, the first force sensor will becomposed of only one force sensor, so that the total sum of the forcedetection values of force sensors constituting the first force sensorwill mean the force detection value itself that is indicated by anoutput of the one force sensor. Further, in the fourth invention, ifeach foot portion is provided with an annular member, as with the secondinvention, then each of the force sensors making up the first forcesensor may be placed between the bottom portion of the annular memberand the sole of the foot, or at the sole of the foot such that it islocated further at the front or the rear relative to the bottom portionof the annular member.

In the third invention described above, a foot supporting member forsupporting a foot of the user may be disposed in the annular member ofeach of the foot-worn assemblies such that it does not come in contactwith the annular member, and the foot supporting member may be suspendedin the annular member through the intermediary of the first force sensor(a fifth invention). The phrase “the foot supporting member is suspendedin the annular member through the intermediary of the first forcesensor” means that the foot supporting member is suspended in theannular member through the intermediary of the first force sensor suchthat no force supporting the foot support member acts from below.

According to the fifth invention, it is possible to apply a force(tensile force) that is as large as a treading force when a leg of theuser becomes a standing leg to the first force sensor between theannular member and the foot supporting member. This allows the treadingforce of the standing leg of the user to be properly measured on thebasis of a force detection value indicated by an output of the firstforce sensor.

The foot supporting member preferably has a plate-shaped portion (soleportion) in contact with substantially the entire bottom surface of thefoot of the user. In this case, for example, both ends of an archedmember are joined to both sides of the sole and the foot of the user isinserted in the arched member from the toe end, and the outer surface ofthe arched member is joined to the inner surface of the annular memberthrough the intermediary of the first force sensor. Furthermore, in thefifth invention, the first force sensor may be composed of a singleforce sensor or it may alternatively be composed of a plurality of forcesensors.

In the first to the fifth inventions, preferably, if a force detectionvalue of the first force sensor of each of the foot-worn assemblies is apredetermined first threshold value or less, then the treading forcemeasuring means sets a measurement value of the treading force of thefoot attached to the foot-worn assembly to zero (a sixth invention).

This arrangement makes it possible to prevent a leg link having thefoot-worn assembly from bearing a lifting force or a weight if a forcedetection value of the first force sensor is very small, that is, if auser does not wish to cause the leg carrying the foot-worn assemblyequipped with the first force sensor to bear the lifting force or theweight. In addition, the influences of minute noises included in forcedetection values of the first force sensor can be removed.

In the first to the sixth inventions, preferably, if a force detectionvalue of the first force sensor of each of the foot-worn assemblies is apredetermined second threshold value or more, then the treading forcemeasuring means obtains a predetermined upper limit value, which is setbeforehand, as the measurement value of a treading force of the footattached to the foot-worn assembly (a seventh invention).

More specifically, a treading force of each leg of a user grasped from aforce detection value of the first force sensor does not smoothly changein general. If the ratio between the treading forces of the two legsfrequently changes, then the desired shares of the leg links alsofrequently change accordingly, often leading to impaired stability ofthe walking assisting device. For this reason, as in the seventhinvention, the measurement values of the treading forces of feet arelimited. This makes it possible to prevent a ratio of the treadingforces of both legs from frequently changing especially in a periodduring which both legs of a user become standing legs (so-called“two-leg supporting period”). Thus, the stability of the walkingassisting device can be enhanced. The second threshold value in theseventh invention is larger than the first threshold value in the sixthinvention. When the sixth invention and the seventh invention are usedin combination, if a force detection value of the first force sensorlies between the first threshold value and the second threshold value,then the measurement value of a treading force may be linearly (lineshape) changed from zero to the aforesaid upper limit value on the basisof detected values of the first force sensor.

Further, in the second invention, preferably, a selector switch forinstructing whether the lifting force control is to be carried out isprovided, and if the operation state of the selector switch is anoperation state instructing that the lifting force control should becarried out, then the desired lifting share determining means multipliesa treading force of each leg of a user by the desired assist ratio todetermine a desired lifting share of the left leg link and a desiredlifting share of the right leg link, or if the operation state of theselector switch is an operation state instructing that the lifting forcecontrol should not be carried out, then the desired lifting sharedetermining means determines an actual assist ratio of a force actuallysupplied by the walking assisting device out of a total treading forceof the user, the actual assist ratio indicating a ratio relative to thetotal treading force, by using a force-to-be-controlled of each leg linkmeasured by the force-to-be-controlled measuring means and a treadingforce of each leg of the user measured by the treading force measuringmeans, and then uses the determined actual assist ratio in place of thedesired assist ratio to determine the desired lifting share of the leftleg link and the desired lifting share of the right leg link (an eighthinvention).

According to the eighth invention, if the operation state of theselector switch is the operation state instructing not to carry out thelifting force control, then an actual assist ratio of a force actuallysupplied by the walking assisting device out of a total treading forceof the user, the actual assist ratio indicating a ratio relative to thetotal treading force, is determined on the basis of a treading force ofeach leg of the user measured by the treading force measuring means anda force-to-be-controlled of each leg link measured by theforce-to-be-controlled measuring means, and then the determined actualassist ratio is used in place of the desired assist ratio to determinethe desired lifting share of the left leg link and the desired liftingshare of the right leg link. In other words, the measured treading forceof each leg of the user is multiplied by the actual assist ratio todetermine the desired lifting share of each leg link. Hence, an actualassist ratio always coincides with a desired assist ratio. Basically,therefore, a load acting on the seating part from the user and a liftingforce acting on the user from the seating part always counterbalancewith each other in a balanced state, and the vertical position of theseating part is retained in that state. This enables the user to easilysit on the seating part. To determine an actual assist ratio,specifically, the supporting force required to support the weight X orthe total weight of the walking assisting device (a supporting forcethat balances out the gravity corresponding to the weight X or the totalweight) may be subtracted from the total sum of theforce-to-be-controlled of each leg link measured on both leg links todetermine an actual lifting force from the seating part to the user, andthe ratio of the actual lifting force relative to the total sum of theforce-to-be-controlled of each leg link of the user that has beenmeasured on both leg links (total treading force) may be determined asthe actual assist ratio.

Then, in this state, if the operation state of the selector switchbecomes the operation state instructing that the lifting force controlbe carried out, then a lifting force corresponding to the desired assistratio that has been set (a lifting force corresponding to a forceobtained by multiplying the total treading force of the user by thedesired assist ratio) will act on the user from the seating part, thuspermitting smooth change to a mode in which a desired lifting force actson the user. Incidentally, according to the eighth invention, thetechnical configurations of the third to the seventh inventionsdescribed above may be combined.

A ninth invention and a tenth invention of the present invention relateto a control program of a walking assisting device. The ninth inventionrelates to a control program that causes a computer for controlling awalking assisting device equipped with a seating part that receives fromabove a part of the weight of a user sitting thereon, a pair of rightand left thigh frames respectively joined to the seating part throughthe intermediary of first joints, a pair of right and left crus framesrespectively joined to the thigh frames through the intermediary ofsecond joints, a pair of right and left foot-worn assemblies that arerespectively joined to the crus frames through the intermediary of thirdjoints, respectively attached to the feet of the right and left legs ofthe user, and come in contact with the ground when the legs of the userbecome standing legs, an actuator for the left for driving a secondjoint among joints of the left leg link composed of the first joint, thethigh frame, the second joint, the crus frame, the third joint, and thefoot-worn assembly on the left side, an actuator for the right fordriving a second joint among joints of the right leg link composed ofthe first joint, the thigh frame, the second joint, the crus frame, thethird joint, and the foot-worn assembly on the right side, and a firstforce sensor provided in each of the foot-worn assemblies for measuringa treading force of each leg of the user, to carry out:

processing for capturing an output of the first force sensor andmeasuring a treading force to be actually applied by the user to a floorsurface from the foot of each of his/her legs on the basis of a forcedetection value indicated by the output;

processing for capturing a set value of a desired assist ratio, which isa desired value of a ratio of a force to be supplied by the walkingassisting device in a total treading force, which is the total sum ofthe treading forces of the legs of the user, relative to the totaltreading force, and multiplying the measured treading force of each legof the user by the set value of the desired assist ratio so as todetermine a desired lifting share that is a desired value of a share ofthe left leg link and a desired lifting share that is a desired value ofa share of the right leg link in the upward lifting force to be appliedto the user from the seating part; and

processing for generating a control output to control the actuator forthe left such that the lifting force to be actually imparted to theseating part from the left leg link becomes the desired lifting share ofthe left leg link that has been determined and also generating a controloutput to control the actuator for the right such that the lifting forceto be actually imparted to the seating part from the right leg linkbecomes the desired lifting share of the right leg link that has beendetermined.

According to the control program of the ninth invention, the actuatorswill be controlled by a computer as in the aforesaid first invention.Thus, a lifting force corresponding to a force obtained by multiplyingthe total treading force of the user by the desired assist ratio can beapplied to the user from the seating part, while dividing the liftingforce between the right and left leg links so as to match a motion stateof each leg desired by the user. As a result, a load on each leg of theuser can be effectively reduced.

Thus, according to the ninth invention, as with the first invention, theforce required for a user to support himself/herself with his/her leg orlegs on a floor can be reduced, while using fewer members to be attachedto each leg of the user, and an assisting force (lifting force) forachieving such a reduction can be properly shared by the leg linksassociated with the individual legs of the user.

Further, a tenth invention relates to a control program that causes acomputer for controlling a walking assisting device equipped with aseating part that receives from above a part of the weight of a usersitting thereon, a pair of right and left thigh frames respectivelyjoined to the seating part through the intermediary of first joints, apair of right and left crus frames respectively joined to the thighframes through the intermediary of second joints, a pair of right andleft foot-worn assemblies that are respectively joined to the crusframes through the intermediary of third joints, respectively attachedto the feet of the right and left legs of the user, and come in contactwith the ground when the legs of the user become standing legs, anactuator for the left for driving a second joint among the joints of theleft leg link composed of the first joint, the thigh frame, the secondjoint, the crus frame, the third joint, and the foot-worn assembly onthe left side, an actuator for the right for driving a second jointamong the joints of the right leg link composed of the first joint, thethigh frame, the second joint, the crus frame, the third joint, and thefoot-worn assembly on the right side, a first force sensor provided ineach of the foot-worn assemblies for measuring a treading force of eachleg of the user, and a second force sensor installed between the lowerend portion of the crus frame and the third joint of each leg link orbetween the third joint and the foot-worn assembly of each leg link tocarry out:

processing for capturing an output of the first force sensor andmeasuring a treading force to be actually applied to a floor surface bythe user from the foot of each of his/her legs on the basis of a forcedetection value indicated by the output;

processing for capturing an output of the second force sensor andmeasuring, as a force-to-be-controlled, a force to be actuallytransmitted from the floor to the crus frame of each leg link on thebasis of a force detection value indicated by the output;

processing for capturing a set value of a desired assist ratio, which isa desired value of a ratio of a force to be supplied by the walkingassisting device in a total treading force, which is the total sum ofthe treading forces of the legs of the user, relative to the totaltreading force, and multiplying the measured treading force of each legof the user by the set value of the desired assist ratio so as todetermine a desired lifting share that is a desired value of a share ofthe left leg link and a desired lifting share that is a desired value ofa share of the right leg link in the upward lifting force to be appliedto the user from the seating part;

processing for distributing a supporting force required to support, on afloor, the weight obtained by subtracting the total weight of theportions below the second force sensors of the walking assisting devicefrom the total weight of the walking assisting device or a supportingforce required to support, on the floor, the total weight of the walkingassisting device to the leg links on the basis of a ratio between atreading force of the left leg and a treading force of the right leg ofthe user, which have been measured, thereby determining a share of theleft leg link and a share of the right leg link out of the supportingforce as the desired device supporting force shares of the respectiveleg links;

processing for determining the total sum of the desired lifting share ofthe left leg link and the desired device supporting force share, whichhave been determined, as the desired value of the force-to-be-controlledof the left leg link, and also determining the total sum of the desiredlifting share of the right leg link and the desired device supportingforce share, which have been determined, as the desired value of theforce-to-be-controlled of the right leg link; and

processing for generating a control output to control the actuator forthe left on the basis of the force-to-be-controlled of the left leglink, which has been measured, and a desired value of theforce-to-be-controlled of the left leg link, which has been determined,such that the difference between the force-to-be-controlled and thedesired value of the left leg link approximates zero and for generatinga control output to control an actuator for the right on the basis of aforce-to-be-controlled of the right leg link, which has been measured,and a desired value of the force-to-be-controlled of the right leg link,which has been determined, such that the difference between theforce-to-be-controlled and the desired value of the right leg linkapproximates zero.

According to the tenth invention, the actuators will be controlled by acomputer, as in the aforesaid second invention. Thus, a lifting forcecorresponding to a force obtained by multiplying the total treadingforce of the user by the desired assist ratio can be properly applied tothe user from the seating part, while considering the weight of thewalking assisting device, by dividing the lifting force between theright and left leg links so as to match a motion state of each legdesired by the user. As a result, a load on each leg of the user can befurther effectively reduced.

Thus, according to the tenth invention, as with the second invention,the force required for a user to support himself/herself with his/herleg or legs on a floor can be reduced, while using fewer members to beattached to each leg of the user, and an assisting force (lifting force)for achieving such a reduction can be properly shared by the leg linksassociated with the individual legs of the user.

In the ninth invention and the tenth invention, the walking assistingdevice is preferably equipped with annular members, as with the thirdinvention. In this case, as with the fifth invention, the footsupporting member may be provided and the foot supporting member may besuspended in the annular member through the intermediary of the firstforce sensor. In such a case, the first force sensor may be composed ofa single force sensor or it may alternatively be composed of a pluralityof force sensors.

In the ninth invention and the tenth inventions, preferably, the firstforce sensor of each of the foot-worn assemblies is composed of one ormore force sensors provided on each foot-worn assembly such that, wheneach leg of the user becomes a standing leg, they lie between at leastat one of the location of the metatarsophalangeal joint and the locationof the heel of the foot on the bottom surface of the foot of thestanding leg and a floor, and the processing for measuring the treadingforce is preferably the processing for taking the total sum of the forcedetection values indicated by outputs of the force sensors constitutingthe first force sensor of each foot-worn assembly as the force detectionvalue of the first force sensor and measuring the treading force of theleg of the user, to which the foot-worn assembly has been attached, onthe basis of the force detection value of the total sum (an eleventhinvention).

According to the eleventh invention, the treading forces of the legs canbe properly measured, as with the fourth invention described above.Especially when force sensors are provided at both the location of themetatarsophalangeal joint and the location of the heel of the foot onthe bottom surface of a foot of the user (more generally, in a casewhere a plurality of force sensors, including the two force sensor, areprovided), the treading force of each leg can be properly measuredregardless of the posture of each foot of the user relative to a floor.

Furthermore, in the ninth to the eleventh inventions, the processing formeasuring treading forces is preferably the processing for setting themeasurement value of a treading force of the foot having the foot-wornassembly attached thereto to zero if a force detection value of thefirst force sensor of each of the foot-worn assemblies is apredetermined first threshold value or less (a twelfth invention).

According to the twelfth invention, as with the sixth invention, it ispossible to prevent a leg link from bearing a lifting force or a weightif a force detection value of the first force sensor is extremely small.In addition, the influences of minute noises included in force detectionvalues of the first force sensor can be removed.

Furthermore, in the ninth to the twelfth inventions, the processing formeasuring treading forces is preferably the processing for obtaining apredetermined upper limit value, which is set beforehand, as themeasurement value of a treading force of the foot having the foot-wornassembly attached thereto if a force detection value of the first forcesensor of each of the foot-worn assemblies is a predetermined secondthreshold value or more (a thirteenth invention).

With this arrangement, as with the seventh invention, it is possible toprevent the ratio of the treading forces of the two legs from frequentlychanging especially in a period during which both legs of a user becomestanding legs (a so-called “two-leg supporting period”). Hence, enhancedstability of the walking assisting device can be achieved. The secondthreshold value in the thirteenth invention is larger than the firstthreshold value in the twelfth invention. When the twelfth invention andthe thirteenth invention are used in combination, if a force detectionvalue of the first force sensor lies between the first threshold valueand the second threshold value, the measurement value of a treadingforce may be linearly (line shape) changed from zero to the upper limitvalue according to detected values of the first force sensor.

Furthermore, in the aforesaid tenth invention, preferably, a selectorswitch for instructing whether or not to carry out the lifting forcecontrol is provided in the walking assisting device, and the processingfor determining the desired lifting share of each leg link is theprocessing for multiplying the measured treading force of each leg ofthe user by the set value of the desired assist ratio to determine adesired lifting share of the left leg link and a desired lifting shareof the right leg link in an upward lifting force to be applied to theuser from the seating part if the operation state of the selector switchis an operation state instructing to carry out the lifting forcecontrol, or for determining an actual assist ratio of a force actuallybeing supplied by the walking assisting device out of a total treadingforce of the user, the actual assist ratio indicating a ratio relativeto the total treading force, by using the measuredforce-to-be-controlled of each leg link and the measured treading forceof each leg of the user, and then determining the desired lifting shareof the left leg link and the desired lifting share of the right leg linkby using the determined actual assist ratio in place of the desiredassist ratio if the operation state of the selector switch is anoperation state instructing not to carry out the lifting force control(a fourteenth invention).

With this arrangement, as with the aforesaid eighth invention, when theoperation state of the selector switch is the operation stateinstructing not to carry out the lifting force control, a load acting onthe seating part from the user and a lifting force acting on the userfrom the seating part always counterbalance with each other in abalanced state, thus enabling the user to easily sit on the seatingpart. Then, in this state, if the operation state of the selector switchchanges to the operation state instructing that the lifting forcecontrol be carried out, then a lifting force corresponding to thedesired assist ratio that has been set will act on the user from theseating part, thus permitting smooth change to a mode in which a desiredlifting force acts on the user. Incidentally, according to thefourteenth invention, the technical configurations of the eleventh tothe thirteenth inventions described above may be combined.

Supplementally, in the first to the fourteenth inventions explainedabove, the seating part may be formed of, for example, a part (e.g., asaddle-like part) over which a user rides and sits thereon (the usersits on the seating part, the seating part being positioned at theproximal ends of both legs of the user). In this case, the first jointof each leg link is preferably provided under the seating part. Thefirst joint of each leg link is preferably a joint having a degree offreedom of rotation about at least two axes so that each leg link mayperform, for example, adduction/abduction motions and longitudinal swingmotions. The second joint of each leg link may be a joint having adegree of freedom of rotation about, for example, a single axis in thelateral direction, or it may be a translatory joint. The third joint ofeach leg link is preferably a joint having a degree of freedom forrotation about three axes.

BEST MODE FOR CARRYING OUT THE INVENTION

The following will explain a first embodiment of the present inventionwith reference to the drawings.

First, the construction of a walking assisting device according to thepresent embodiment will be explained by referring to FIG. 1 to FIG. 3.FIG. 1 is a side view of a walking assisting device 1, FIG. 2 is asagittal view taken at II in FIG. 1, and FIG. 3 is a sectional viewtaken at III-III in FIG. 1. The walking assisting device 1 in these FIG.1 to FIG. 3 is shown in a state wherein it is in operation while beingattached to a user A (indicated by virtual lines). In this case, theuser A shown in the figures is standing virtually in an upright posture.However, in FIG. 2, the user A takes a posture in which the user's bothlegs are laterally spread in order to make it easier to see theconstruction of the walking assisting device 1.

Referring to FIG. 1 and FIG. 2, the walking assisting device 1 is aweight bearing assisting device for supporting a part of the weight ofthe user A (for making the weight supported by the legs (standing legs)of the user lighter than the weight of himself/herself). The walkingassisting device 1 includes a seating part 2 on which the user A sitsand a pair of right and left leg links 3R and 3L connected to theseating part 2. The leg links 3L and 3R share the same structure. InFIG. 1, the leg links 3L and 3R are in the same posture and arranged inthe lateral direction (in the direction perpendicular to the papersurface of FIG. 1) of the user A, and they overlap in the drawing inthis state (the leg link 3L on the left is positioned on the front sideof the figure).

In the explanation of the embodiments in the present description, acharacter “R” will be used to mean the relation to the right leg of theuser A or a leg link 3R on the right side of the walking assistingdevice 1, and a character “L” will be used to mean the relation to theleft leg of the user A or a leg link 3L on the left side of the walkingassisting device 1. If, however, there is no need to particularlydistinguish between right and left, then the characters R and L will befrequently omitted.

The seating part 2 is a saddle-shaped member that enables the user A tostride over the seating part 2 (with the seating part 2 positioned atthe proximal ends of both legs of the user A) and sit on the uppersurface (seating parting surface) of the seating part 2. When the user Ais seated as described above, a part of the weight of the user A isimparted to the seating part 2 from above.

As shown in FIG. 1, a front end 2 f and a rear end 2 r of the seatingpart 2 protrude upward, as shown in FIG. 1. This arrangement restricts aseating parting position (a longitudinal position) of the user Arelative to the seating part 2 between the front end 2 f and the rearend 2 r of the seating part 2. The front end 2 f of the seating part 2has a bifurcated shape, as shown in FIG. 2.

Each leg link 3 has a thigh frame 11 connected to the bottom surface ofthe seating part 2 through the intermediary of a first joint 10, a crusframe 13 connected to the thigh frame 11 through the intermediary of asecond joint 12, and a foot-worn assembly 15 connected to the crus frame13 through the intermediary of a third joint 14.

The first joint 10 of each leg link 3 is a joint corresponding to a hipjoint of the user A and it permits a swinging motion of the leg link 3about a lateral axis (a longitudinal swinging motion of the leg link 3)and a swinging motion thereof about a longitudinal axis(adduction/abduction motions). The first joint 10 is located below theseating part 2. The first joint 10 includes a pair of shaft pins 20 fand 20 r that are disposed at a location adjacent to the front and atthe rear end location of the bottom surface of the seating part 2 andcoaxially disposed on a longitudinal axis C indicated by a dashed linein FIG. 1, brackets 21 f and 21 r rotatively supported by the shaft pins20 f and 20 r, respectively, an arc-shaped guide rail 22 fixed to thebottom ends of the brackets 21 f and 21 r, and a plate 23 movablysupported by the guide rail 22 along the guide rail 22. Further, thethigh frame 11 is extended from the plate 23 aslant forward anddownward. The thigh frame 11 is an approximately rod-shaped member madeintegrally with the plate 23.

Both ends (front and rear ends) of each of the shaft pins 20 f and 20 rare fixed to the seating part 2 through the intermediary of bearings 24f and 24 r secured to the bottom surface of the seating part 2. Theupper end of the bracket 21 f is supported by the shaft pin 20 f bybeing fitted in the outer periphery of the middle portion of the shaftpin 20 f. This allows the bracket 21 f to freely rotate about the axis Cof the shaft pin 20 f. Similarly, the upper end of the bracket 21 r issupported by the shaft pin 20 r by being fitted in the outer peripheryof the middle portion of the shaft pin 20 r. This allows the bracket 21r to freely rotate about the axis C of the shaft pin 20 r. Thus, theguide rail 22 of each first joint 10 swings together with the brackets21 f and 21 r, using the axis C of the shaft pins 20 f and 20 r as therotational axis. In the present embodiment, the first joints 10R and 10Lof the leg links 3R and 3L, respectively, share the same rotational axisC, the shaft pins 20 f and 20 r being shared by the first joint 10R ofthe leg link 3R and the first joint 10L of the leg link 3L. Morespecifically, a bracket 21 fR of the right first joint 10R and a bracket21 fL of the left first joint 10L are supported by the same shaft pin 20f. Similarly, a bracket 21 rR of the right first joint 10R and a bracket21 rL of the left first joint 10L are supported by the same shaft pin 20r.

The plate 23 of the first joint 10 of each leg link 3 is disposedadjacently to the guide rail 22 and oriented in parallel to a plane thatincludes the arc of the guide rail 22. A carrier 26 having a pluralityof (e.g., four) rotative rollers 25 is secured to the plate 23, as shownin FIG. 1. The same number of the rollers 25 of the carrier 26 engageswith the upper surface (inner peripheral surface) and the lower surface(outer peripheral surface), respectively, of the guide rail 22 in such amanner that they are free to roll. This allows the plate 23 to freelymove along the guide rail 22. In this case, the positional relationshipbetween the guide rail 22 and the seating part 2 and the radius of thearc of the guide rail 22 are set such that a central point P of the arcof the guide rail 22 is located above the seating part 2 when thewalking assisting device 1 is observed in a sagittal plane, as shown inFIG. 1.

The construction of the first joint 10 explained above allows the thighframe 11 made integral with the plate 23 to swing about the longitudinalrotational axis C of the user A. This swing motion permits theadduction/abduction motions of each of the leg links 3. The thigh frame11 made integral with the plate 23 is free to swing about the lateralaxis passing the central point P (more accurately, about the axis thatis perpendicular to the plane that includes the arc of the guide rail 22and that passes the central point P). This swing motion allows the leglinks 3 to swing back and forth. In the present embodiment, the firstjoint 10 is a joint that permits rotational motions about two axes, oneaxis in the longitudinal direction and the other axis in the lateraldirection. Alternatively, however, the first joint may be constructedsuch that it permits rotational motions about a vertical axis (inwardand outward turning motions of the leg links 3) in addition to therotational motions about the two axes, namely, the axis in thelongitudinal direction and the axis in the lateral direction (i.e., suchthat it permits rotational motions about three axes). Alternatively, thefirst joint may be a joint that permits only the rotational motionsabout one axis in a lateral direction (a joint that allows each of theleg links 3 to swing back and forth only).

The plate 23 of the first joint 10 of each leg link 3 extends from thelocation of the carrier 26 toward the rear of the seating part 2 whenthe walking assisting device 1 is observed in the sagittal plane, asshown in FIG. 1. At the rear end of the plate 23, an electric motor 27and a rotary encoder 28 serving as a rotation angle detecting means fordetecting a rotation angle (a rotation angle from a predeterminedreference position) of the rotor of the electric motor 27 are coaxiallyinstalled. In the present embodiment, the second joint 12 among thefirst to the third joints 10, 12, and 14, respectively, of each leg link3 is driven. The electric motor 27 is an actuator that drives the secondjoint 12. A rotation angle detected by the rotary encoder 28 is used formeasuring a rotation angle (a bend angle) of the second joint 12. Anelectric motor 27L of the left leg link 3L and an electric motor 27R ofthe right leg link 3R correspond to the actuator for the left and theactuator for the right, respectively, in the present invention. Eachrotary encoder 28 corresponds to the displacement amount sensor in thepresent invention. Each actuator may be a hydraulic or pneumaticactuator. Further, each actuator may be fixed to, for example, the rearportion of the seating part 2 through the intermediary of an appropriatebracket. Alternatively, each actuator may be attached to the secondjoint 12 of each leg link 3 to directly drive the second joint 12. Thedisplacement amount sensor may be directly attached to the second joint12 of each leg link 3. Further alternatively, the displacement amountsensor may be composed of a potentiometer or the like in place of arotary encoder.

The second joint 12 of each leg link 3 is a joint that corresponds to aknee joint of the user A and enables the leg link 3 to bend and stretch.The second joint 12 connects the lower end of the thigh frame 11 and theupper end of the crus frame 13 through the intermediary of a shaft pin29 having an axis in the lateral direction (more accurately, an axis inthe direction perpendicular to a plane that includes the arc of theguide rail 22). The second joint 12 allows the crus frame 13 to freelyand relatively rotate about the axis of the shaft pin 29 with respect tothe thigh frame 11. The second joint 12 is provided with a stopper, notshown, for restricting the range in which the crus frame 13 can rotaterelative to the thigh frame 11.

The crus frame 13 of each leg link 3 is an approximately rod-shapedmember extending aslant downward from the second joint 12 of the leglink 3. More specifically, the crus frame 13 is formed by connecting alower crus frame 13 b, which constitutes a portion adjacent to the thirdjoint 14, and a rod-shaped upper crus frame 13 a, which constitutes aportion above the lower crus frame 13 b, through the intermediary of aforce sensor 30 (corresponding to the second force sensor in the presentinvention) located therebetween. The lower crus frame 13 b issufficiently shorter than the upper crus frame 13 a. Thus, the forcesensor 30 is disposed adjacently to the third joint 14. The force sensor30 is a force sensor called “Kistler Sensor” (registered trademark).More specifically, the force sensor 30 is a three-axis force sensor fordetecting the translational forces of three axes (a translational forcein the axial direction perpendicular to the surface of the force sensor30 and the translational forces in two axial directions that areparallel to the surface and that are orthogonal to each other). In thepresent embodiment, however, only the detection values of thetranslational forces of two axes out of the translational forces ofthree axes that are detected are used. Therefore, the force sensor 30may be composed of a two-axis force sensor adapted to detecttranslational forces of two axes.

A pulley 31 that is rotatively integral with the crus frame 13 about theshaft pin 29 of the second joint 12 is secured to the upper end of theupper crus frame 13 a of the crus frame 13. The ends of a pair of wires32 a and 32 b serving as a driving force transmitting means fortransmitting a rotational driving force of the electric motor 27 to thepulley 31 are secured to the outer periphery of the pulley 31. Thesewires 32 a and 32 b are drawn out in the tangential direction of thepulley 31 from two places opposing the diametral direction of the outerperiphery of the pulley 31. The wires 32 a and 32 b are run through arubber hose (protective tube of the wires), not shown, which is laidalong the thigh frame 11, and connected to a rotational drive shaft (notshown) of the electric motor 27. In this case, the electric motor 27applies tensions to these wires 32 a and 32 b such that one of the wires32 a and 32 b is rewound by the pulley 31, while the other is drawn outof the pulley 31 when the rotational drive shaft of the electric motor27 rotates in the forward direction, and one of the wires 32 a and 32 bis rewound by the pulley 31, while the other is drawn out of the pulley31 when the rotational drive shaft of the electric motor 27 rotates inthe reverse direction. Thus, the rotational driving force of theelectric motor 27 is transmitted to the pulley 31 through theintermediary of the wires 32 a and 32 b such that the pulley 31 isrotationally driven (such that the crus frame 13, to which the pulley 31is secured, rotates about the axis of the shaft pin 29 of the secondjoint 12 relative to the thigh frame 11).

The bottom end of the lower crus frame 13 b of the crus frame 13 has abifurcated tip 13 bb formed to have a bifurcated shape, as shown in FIG.3.

The third joint 14 of each leg link 3 is a joint corresponding to anankle joint of the user A. The third joint 14 is composed of a freejoint 33 (refer to FIG. 3) that permits rotations about three axes, asshown in FIG. 3. The free joint 33 is attached to the bifurcated tip 13bb of the lower crus frame 13 b of the crus frame 13 to connect thelower end (the bifurcated tip 13 bb) of the crus frame 13 and a joiningportion 34 on the top of the foot-worn assembly 15. This enables thefoot-worn assembly 15 to rotate with three degrees of freedom relativeto the crus frame 13. The range of rotation of the foot-worn assembly 15about a longitudinal axis is restricted by the bifurcated tip 13 bb ofthe crus frame 13.

The foot-worn assembly 15 of each leg link 3 includes a shoe 35 intowhich a foot of the user A is to be placed and a stirrup-shaped annularmember 36 housed in the shoe 35, the annular member 36 having its upperend secured to the joining portion 34. As shown in FIG. 3, the annularmember 36 is housed in the shoe 35 such that the flat bottom platethereof is abutted against the internal bottom surface of the shoe 35and the curved portion thereof extending to both ends of the bottomplate is abutted against the side wall of the cross section of the shoe35. Further, a sole insert member 37 made of a rigid plate (not shown inFIG. 1) is inserted in the shoe 35 such that it covers the internalbottom surface of the shoe 35 and the bottom plate of the annular member36. The joining portion 34 is inserted in the shoe 35 through an openingfor inserting a shoelace of the shoe 35.

To put the foot-worn assembly 15 of each leg link 3 on each foot of theuser A, the foot of the user A is inserted in the shoe 35 from the topopening of the shoe 35 by passing the toe portion of the foot throughthe annular member 36 and by placing the sole insert member 37 on thebottom surface of the foot. Then, in this state, the shoelace istightened up, thus attaching the foot-worn assembly 15 onto the foot.

On the bottom surface of the sole insert member 37 of the foot-wornassembly 15, force sensors 38 and 39 are installed at a location on thefront side of the shoe 35 (a location farther to the front than thebottom plate of the annular member 36) and at a location on the rearside thereof (a location farther to the rear than the bottom plate ofthe annular member 36). The force sensor 38 on the front side isdisposed such that it is substantially right below an MP joint(metatarsophalangeal joint) of the foot of the user A wearing thefoot-worn assembly 15. The force sensor 39 on the rear side is disposedsuch that it is substantially right below the heel of the foot. In thepresent embodiment, these force sensors 38 and 39 are one-axis forcesensors for detecting translational forces in a direction perpendicularto the bottom surface (ground contact surface) of the foot-worn assembly15 (a direction substantially perpendicular to a floor surface in astate wherein a leg or legs of the user A are standing). Hereinafter,the force sensors 38 and 39 will be referred to as the MP sensor 38 andthe heel sensor 39, respectively. The MP sensor 38 and the heel sensor39 constitute the first force sensor in the present invention. The soleinsert member 37 does not necessarily have to be a rigid plate; it mayalternatively be formed of a soft (flexible) material. If the soleinsert member 37 is formed of a soft material, providing the bottomsurface thereof with a plurality of first force sensors permits highlyaccurate detection of a force applied to each portion of the bottomsurface of a foot of the user A. Meanwhile, if the sole insert member 37is formed of a rigid plate, then a treading force of an entire foot ofthe user A can be easily detected. This makes it possible to reduce thenumber of the first force sensors installed on the bottom surface of thesole insert member 37.

The above describes the construction of the walking assisting device 1according to the present embodiment. Supplementally, in a state whereinthe foot-worn assembly 15 has been attached to each foot of the user Aand the user A sits on the seating part 2 with the walking assistingdevice 1 in operation (while the second joint 12 is being driven by theelectric motor 27), as it will be discussed later, if the user A and thewalking assisting device 1 are observed in a frontal plane (observedfrom the front side of the user A), the thigh frame 11L of the left leglink 3L, for example, extends along the inner surface of the left leg ofthe user A (see FIG. 2), and the second joint 12L at the bottom end ofthe thigh frame 11L is positioned on the inner side of the left leg.Although not shown, the upper portion of the crus frame 13L (the upperportion of the upper crus frame 13L) connected to the second joint 12Lis formed such that it extends along the inner surface of the left legof the user A from the second joint 12L when observed in a frontal planeand that the lower portion thereof gradually curves and reaches a pointright above the instep of the foot of the left leg in front of the shinof the left leg. The same applies to the right leg link 3R.

When the user A having a typical build stands up in an upright posture,the second joints 12 of the leg links 3 jut out toward the front beyondthe legs of the user A, as shown in FIG. 1. More specifically, thelengths of the thigh frame 11 and the crus frame 13 are set such thatthe sum of the lengths is slightly greater than the dimension of theinseam of a leg of the user A having a typical build. The lengths of thethigh frame 11 and the crus frame 13 set as described above and thestopper of the second joint 12 described above restrain the occurrenceof a singular point state in which the thigh frame 11 and the crus frame13 are aligned or a state in which the thigh frame 11 and the crus frame13 bend in the opposite direction from that shown in FIG. 1. Thisrestrains the control of the walking assisting device 1 from failing dueto the singular point state or the reverse bend state of the leg links3.

The second joint of each leg link 3 may be a translatory joint.

Although the details will be discussed later, in the walking assistingdevice 1 constructed as described above, an upward lifting force isapplied from the seating part 2 to the user A by generating torques ofthe second joints 12 by the electric motors 27, with the foot-wornassemblies 15 being attached to the feet of the legs of the user A. Atthis time, if, for example, both legs of the user A are standing legs(the legs to support the weight of the user A)(in the so-called two-legsupporting period), then the foot-worn assemblies 15, 15 on both feetcome in contact with a floor and floor reaction forces act on therespective ground contact surfaces. The floor reaction forces acting onthe ground contact surfaces of the foot-worn assemblies 15 are such thatthe resultant force thereof is a force that balances out the sum of thegravity acting on the user A and the gravity acting on the walkingassisting device 1, that is, the force for supporting the total weightof the user A and the walking assisting device 1 on a floor (thetranslational force, which will be hereinafter referred to as “the totalsupporting force”). More accurately, when the legs of the user A are inmotions together with the leg links 3 of the walking assisting device 1,a force for supporting an inertial force generated by the motions of theuser A and the walking assisting device 1 will be added to the totalsupporting force; however, in the walking assisting device 1 accordingto the present embodiment, the electric motors 27 (actuators) and theencoders 28 having large weights are disposed in the vicinity of thewaist rather than in the vicinity of the knees of the leg links 3. Onlythe foot-worn assemblies 15 of the leg links 3 are restricted (worn) bythe user A, so that the number of members to be attached to the user Ais smaller, making the leg links 3 lighter. Thus, an inertial force froma motion of the walking assisting device 1 remains sufficiently small.In the present embodiment, the weight of the user A means the totalweight that includes the clothing (anything on the body) and belongingsof the user A. The gravity acting on the user A means the gravitycorresponding to the total weight of the user A (the product of thetotal weight and a gravitational acceleration constant).

In this case, in the walking assisting device 1 according to the presentembodiment, only the two foot-worn assemblies 15 and 15 are restrainedby being attached to the user A. Each foot-worn assembly 15 includes theannular link member 36. Therefore, the gravity acting on the walkingassisting device 1 and the load received by the walking assisting device1 from the user A (a downward translational force) through theintermediary of the seating part 2 hardly act on the user A; instead,they act on a floor surface from the two leg links 3, 3 through theintermediary of the annular link members 36, 36 of the two foot-wornassemblies 15, 15, respectively.

Accordingly, both leg links 3, 3 of the walking assisting device 1 aresubjected to a supporting force for supporting the gravity acting on thewalking assisting device 1 and a load received by the walking assistingdevice 1 from the user A through the intermediary of the seating part 2out of the total supporting force. The supporting force is borne by thewalking assisting device 1 through the intermediary of the two leg links3, 3. Hereinafter, the supporting force borne by the walking assistingdevice 1 as described above will be referred to as “theborne-by-the-assisting-device supporting force.” In other words, theborne-by-the-assisting-device supporting force is a supporting force forsupporting the weight of the entire walking assisting device 1 and aweight corresponding to a load received by the seating part 2 from theuser A (a part of the weight of the user A) on a floor. If both legs ofthe user A are standing (if both foot-worn assemblies 15 of the walkingassisting device 1 are in contact with the ground), then theborne-by-the-assisting-device supporting force is dividedly borne by thetwo leg links 3, 3 (a part of the borne-by-the-assisting-devicesupporting force is borne by one leg link 3 and the rest thereof isborne by the other leg link 3). If only one leg of the user A isstanding (if the other leg is free), then all theborne-by-the-assisting-device supporting force is borne by the standingleg link 3. Hereinafter, the supporting force borne by one of the leglinks 3 (the supporting force acting on one of the leg links 3) out ofthe borne-by-the-assisting-device supporting force will be referred toas “the borne-by-the-leg-link supporting force.” Further, a supportingforce borne by the right leg link 3 will be referred to as “theborne-by-the-right-leg-link supporting force” and a supporting forceborne by the left leg link 3 will be referred to as “theborne-by-the-left-leg-link supporting force.” The total sum of theborne-by-the-left-leg-link supporting force and theborne-by-the-right-leg-link supporting force coincides with theborne-by-the-assisting-device supporting force.

Meanwhile, a supporting force, which is obtained by subtracting theborne-by-the-assisting-device supporting force from the total supportingforce, acts from the floor surface to both legs of the user A, and thissupporting force is borne by the user A with his/her legs. Hereinafter,the supporting force borne by the user A will be referred to as “theborne-by-the-user supporting force.” In other words, theborne-by-the-user supporting force is a supporting force for supportingthe weight, which is obtained by subtracting a weight corresponding to aload to be applied by the user A to the seating part 2 of the walkingassisting device 1 from the weight of the user A, on a floor. If bothlegs of the user A are standing, then the borne-by-the-user supportingforce is divided among and borne by both legs of the user A (a part ofthe borne-by-the-user supporting force is borne by one leg and theremainder of the supporting force is borne by the other leg). If onlyone leg of the user A is standing, then all the borne-by-the-usersupporting force is borne by the one leg. Hereinafter, the supportingforce borne by each leg (the supporting force acting on each leg from afloor surface) out of the borne-by-user supporting force will bereferred to as “the borne-by-user-leg supporting force,” and asupporting force borne by the right leg will be referred to as “theborne-by-user-right-leg supporting force” and a supporting force borneby the left leg will be referred to as “the borne-by-user-left-legsupporting force.” The total sum of the borne-by-user-left-legsupporting force and the borne-by-user-right-leg supporting forcecoincides with the borne-by-user supporting force. The force that theuser A applies to push the foot of each leg against a floor surface tosupport himself/herself is referred to as a treading force of the leg.The treading force of each leg balances out the borne-by-user-legsupporting force.

Supplementally, the force sensor 30 provided in each leg link 3 islocated on the third joint 14. Hence, the supporting force, which isobtained by subtracting the supporting force for supporting the weightof the portion below the force sensor 30 (e.g., the foot-worn assembly15) of the leg link 3 from the leg link supporting force related to theleg link 3, acts on the force sensor 30. Then, the components inthree-axis directions (or two-axis directions) of the acting supportingforce are detected by the force sensor 30. In other words, the forceacting on each force sensor 30 (this corresponds to theforce-to-be-controlled in the present invention) corresponds to theshare in the leg link 3 provided with the force sensor 30 out of thetotal supporting force for supporting the weight, which is obtained bysubtracting the total sum of the weights of the portions below the forcesensors 30 from the weight of the entire walking assisting device 1, andthe weight corresponding to a load imparted to the seating part 2 fromthe user A. Further, the total sum of the supporting forces detected bythe two force sensors 30 and 30, respectively, coincides with the totalsupporting force for supporting the weight, which is obtained bysubtracting the total sum of the weights of the portions below the forcesensors 30 from the weight of the entire walking assisting device 1, andthe weight corresponding to a load imparted to the seating part 2 fromthe user A (hereinafter, the force sensors 30 will be referred to as“the supporting force sensors 30”). The total sum of the weights of theportions below the supporting force sensors 30 of the walking assistingdevice 1 is sufficiently small, as compared with the weight of theentire walking assisting device 1. Hence, the supporting force acting oneach of the supporting force sensors 30 is substantially equal to theleg link supporting force. Further, each supporting force sensor 30 isprovided adjacently to the third joint 14 of the leg link 3 providedwith the same. Hence, a supporting force acting on the supporting forcesensor 30 is substantially equal to a translational force acting on thecrus frame 13 from the third joint 14 of the leg link 3 (the supportingforce out of the leg link supporting force that is transmitted from afloor to the crus frame 13 through the intermediary of the third joint14). Hereinafter, the total sum related to both leg links 3 and 3, thatis, the total sum of the supporting forces acting on the supportingforce sensors 30 or the translational forces acting on the crus frames13 from the third joints 14 of the leg links 3 will be referred to as“the total supporting force.” Of the total supporting force, the shareof each leg link 3 will be referred to as “the total supporting forceshare.”

The total sum of the forces acting on the MP sensor 38L and the heelsensor 39L of the left foot-worn assembly 15L corresponds to theaforesaid borne-by-user-left-leg supporting force (or the treading forceof the left leg). Similarly, the total sum of the forces acting on theMP sensor 38R and the heel sensor 39R of the right foot-worn assembly15R corresponds to the aforesaid borne-by-user-right-leg supportingforce (or the treading force of the right leg). In the presentembodiment, the MP sensor 38 and the heel sensor 39 use one-axis forcesensors; however, they may alternatively use, for example, two-axisforce sensors that detect also translational forces in directionssubstantially parallel to the bottom surface of the shoe 33, or they mayuse three-axis force sensors. The MP sensor 38 and the heel sensor 39desirably use sensors capable of detecting translational forces indirections substantially perpendicular at least to the sole of the shoe33 or a floor surface.

The control device of the walking assisting device 1 constructed asdescribed above will now be explained.

FIG. 4 is a block diagram schematically showing the configuration(hardware configuration) of the control device 50. As shown in thefigure, the control device 50 includes an arithmetic processor 51composed of a microcomputer (a CPU, a RAM, and a ROM) and aninput/output circuit (an A/D converter or the like), driver circuits 52Rand 52L for the electric motors 27R and 27L, respectively, an assistratio setting key switch 53 for setting a desired assist ratio, which isa desired value of a ratio relative to the total treading force of theassisting force provided by the walking assisting device 1 in the totaltreading force of the user A, a lifting control ON/OFF switch 54 forselecting whether or not to generate a lifting force for the user A, apower battery 55, and a power circuit 57 that is connected to the powerbattery 55 through the intermediary of a power switch 56 (ON/OFF switch)and supplies power from the power battery 55 to the circuits of 51, 52Rand 52L of the control device 50 when the power switch 56 is turned ON(closed). The assist ratio setting key switch 53 corresponds to thedesired assist ratio setting means in the present invention, and thelifting control ON/OFF switch 54 corresponds to the selector switch inthe present invention.

The control device 50 is secured to the rear end of the seating part 2or the plate 23R or 23L or the like through the intermediary of abracket (not shown). The assist ratio setting key switch 53, the liftingcontrol ON/OFF switch 54, and the power switch 56 are mounted on theouter surface of the housing (not shown) of the control device 50 sothat they are accessible for control. The assist ratio setting keyswitch 53 is formed of a ten-key switch or a plurality of selectorswitches to permit direct setting of a desired target value of an assistratio or selective setting from among a plurality of types of desiredvalues prepared beforehand.

Connected to the control device 50 are the MP sensors 38R, 38L, the heelsensors 39R, 39L, the supporting force sensors 30R, 30L, and the rotaryencoders 28R, 28L via connection lines, which are not shown. The outputsignals of these sensors are supplied to the arithmetic processor 51.The arithmetic processor 51 receives control signals of the assist ratiosetting key switch 53 and the lifting control ON/OFF switch 54 (signalsindicating the operation states of the switches). Further, the controldevice 50 is connected to the electric motors 27R, 27L via connectionlines, which are not shown, to supply current to the electric motors 27Rand 27L from the driver circuits 52R, 52L. The arithmetic processor 51determines the command values of current (hereinafter referred to as“the instructed current values”) for energizing the electric motors 27R,27L by arithmetic processing (control processing) to be described later.The arithmetic processor 51 controls the driver circuits 52R, 52L on thebasis of the instructed current values so as to control the producedtorques of the electric motors 27R, 27L.

Output signals (voltage signals) of the MP sensors 38R, 38L, the heelsensors 39R, 39L, and the supporting force sensors 30R, 30L may beamplified by a preamplifier in the vicinity of these sensors and theninput to the control device 50. The voltage values of the amplifiedoutput signals of the MP sensors 38R, 38L, the heel sensors 39R, 39L,and the supporting force sensors 30R, 30L are subjected to A/Dconversion before the amplified output signals are supplied to thearithmetic processor 51.

The arithmetic processor 51 has a functional mean shown in the blockdiagram of FIG. 5 as its main functional means. The functional means isa function implemented by a program stored in the ROM.

Referring to FIG. 5, the arithmetic processor 51 is provided with aright treading force measurement processing means 60R to which outputsignals of the MP sensor 38R and the heel sensor 39R of the right leglink 3R are supplied and a left treading force measurement processingmeans 60L to which output signals of the MP sensor 38L and the heelsensor 39L of the left leg link 3L are supplied. The right treadingforce measurement processing means 60R is a means for carrying out theprocessing for measuring the magnitude of a treading force of the rightleg of the user A (the magnitude of the borne-by-user-right-legsupporting force) from the voltage values of output signals of the MPsensor 38R and the heel sensor 39R. Similarly, the left treading forcemeasurement processing means 60L is a means for carrying out theprocessing for measuring the magnitude of a treading force of the leftleg of the user A (the magnitude of the borne-by-user-left-legsupporting force) from the voltage values of output signals of the MPsensor 38L and the heel sensor 39L. The treading force measurementprocessing means 60R and 60L correspond to the treading force measuringmeans in the present invention.

The arithmetic processor 51 is equipped with a right knee anglemeasurement processing means 61R and a left knee angle measurementprocessing means 61L to which output signals (pulse signals) of therotary encoders 28R and 28L are supplied. These knee angle measurementprocessing means 61R and 61L are means for measuring the bending anglesin the second joints 12 (the displacement amounts of the second joints12) of the leg links 3 associated therewith. The second joint 12 of eachleg link 3 corresponds to the knee joint of the leg link 3, so that thebending angle in the second joint will be hereinafter referred to as theknee angle.

Further, the arithmetic processor 51 is equipped with a right supportingforce measurement processing means 62R to which output signals of thesupporting force sensor 30R of the right leg link 3R and knee angles ofthe right leg link 3R measured by the right knee angle measurementprocessing means 61R are supplied, and a left supporting forcemeasurement processing means 62L to which output signals (outputvoltages) of the supporting force sensor 30L of the left leg link 3L andknee angles of the left leg link 3L measured by the left knee anglemeasurement processing means 61L are supplied. The right supportingforce measurement processing means 62R is a means that carries out theprocessing for measuring the supporting force acting on the supportingforce sensor 30R out of the right leg link supporting force, i.e., thetotal supporting force share of the right leg link 3R, on the basis of areceived output signal of the supporting force sensor 30R and ameasurement value of a knee angle of the right leg link 3R. Similarly,the left supporting force measurement processing means 62L is a meansthat carries out the processing for measuring the supporting forceacting on the supporting force sensor 30L out of the left leg linksupporting force, i.e., the total supporting force share of the left leglink 3L, on the basis of a received output signal of the supportingforce sensor 30L and a measurement value of a knee angle of the left leglink 3L. These supporting force measurement processing means 62R and 62Lcorrespond to the force-to-be-controlled measuring means in the presentinvention.

The arithmetic processor 51 is equipped with a right/left desired sharedetermining means 63, which receives the measurement values of themeasurement processing means 60R, 60L, 61R, 61L, 62R, and 62L and thecontrol signals of the assist ratio setting key switch 53 and thelifting control ON/OFF switch 54. The right/left desired sharedetermining means 63 is a means that carries out processing fordetermining a desired value of the total supporting force share(hereinafter referred to simply as the control desired value) of eachleg link 3 on the basis of input values. The control desired valuecorresponds to a desired value of a force-to-be-controlled in thepresent invention.

Further, the arithmetic processor 51 is equipped with a right feedbackmanipulated variable determining means 64R that receives a totalsupporting force share of the right leg link 3R measured by the rightsupporting force measurement processing means 62R and a control desiredvalue of the right leg link 3R determined by the right/left desiredshare determining means 63, and a left feedback manipulated variabledetermining means 64L that receives a total supporting force share ofthe left leg link 3L measured by the left supporting force measurementprocessing means 62L and a control desired value of the left leg link 3Ldetermined by the right/left desired share determining means 63, a rightfeedforward manipulated variable determining means 65R that receives thetotal supporting force share of the right leg link 3R measured by theright supporting force measurement processing means 62R, the controldesired value of the right leg link 3R determined by the right/leftdesired share determining means 63, and the knee angle of the right leglink 3R measured by the right knee angle measurement processing means61R, and a left feedforward manipulated variable determining means 65Lthat receives the total supporting force share of the left leg link 3Lmeasured by the left supporting force measurement processing means 62L,the control desired value of the left leg link 3L determined by theright/left desired share determining means 63, and the knee angle of theleft leg link 3L measured by the left knee angle measurement processingmeans 61L. Each of the feedback manipulated variable determining means64 is a means for calculating, according to a predetermined feedbackcontrol law, a feedback manipulated variable (the feedback component ofthe instructed current value relative to each electric motor 27) on thebasis of a difference between a measurement value of an input totalsupporting force share and a control desired value such that thedifference converges to zero. Each of the feedforward manipulatedvariable determining means 65 is a means for calculating, according to apredetermined feedforward control law, a feedforward manipulatedvariable (the feedforward component of the instructed current valuerelative to each electric motor 27) for adjusting the measurement valueof the total supporting force share to a control desired value on thebasis of an input measurement value of a total supporting force share, acontrol desired value, and a measurement value of a knee angle.

In addition, the arithmetic processor 51 is equipped with an additionprocessing means 66R for determining an instructed current value for theelectric motor 27R of the right leg link 3R by adding a feedbackmanipulated variable calculated by the right feedback manipulatedvariable determining means 64R and a feedforward manipulated variablecalculated by the right feedforward manipulated variable determiningmeans 65R, and an addition processing means 66L for determining aninstructed current value for the electric motor 27L of the left leg link3L by adding a feedback manipulated variable calculated by the leftfeedback manipulated variable determining means 64L and a feedforwardmanipulated variable calculated by the left feedforward manipulatedvariable determining means 65L.

The feedback manipulated variable determining means 64R, 64L, thefeedforward manipulated variable determining means 65R, 65L, and theaddition processing means 66R, 66L described above correspond to theactuator controlling means in the present invention.

The above is the overview of the arithmetic processing function of thearithmetic processor 51.

The control processing of the control device 50 according to the presentembodiment will now be explained. This will include detailed explanationof the processing by the arithmetic processor 51. In the walkingassisting device 1 according to the present embodiment, if the powerswitch 56 is OFF, no driving force will be imparted to the second joints12 of the leg links 3, thus allowing the joints 10, 12 and 14 to freelymove. In this state, the leg links 3 are folded due to their ownweights. In this state, each foot-worn assembly 15 is attached to eachfoot of the user A, then the user A or an attendant lifts the seatingpart 2 and positions it under the crotch of the user A.

Subsequently, when the power switch 56 is turned ON, power is suppliedto the circuits of the control device 50, thus activating the controldevice 50. As the control device 50 is activated, the arithmeticprocessor 51 carries out the processing, which will be explained below,at predetermined control processing cycles.

In each control processing cycle, the arithmetic processor 51 firstcarries out the processing of the treading force measurement processingmeans 60R and 60L. This processing will be explained with reference toFIG. 6. FIG. 6 is a block diagram showing the flows of the processing bythe treading force measurement processing means 60R and 60L. Thetreading force measurement processing means 60R and 60L share the samealgorithm of processing, so that any components related to the lefttreading force measurement processing means 60L are shown in parenthesesin FIG. 6.

As representative processing, the processing of the right treading forcemeasurement processing means 60R will be explained. First, a detectionvalue of the MP sensor 38R (the detection value of a force indicated byan output voltage value of the MP sensor 38R) and a detection value ofthe heel sensor 39R (the detection value of a force indicated by anoutput voltage of the heel sensor 39R) of the leg link 3R are passedthrough low-pass filters in S101 and S102, respectively. The low-passfilters remove high-frequency components, such as noises, from thedetection values of the sensors 38R and 39R. The cutoff frequencies ofthe low-pass filters are set to, for example, 100 Hz.

Subsequently, the outputs of the low-pass filters are added in S103.This provides a provisional measurement value FRF_p_R of the treadingforce of the right leg of the user A. The provisional measurement valueFRF_p_R contains an error component resulting mainly from the tighteningof the shoelace of the right foot-worn assembly 15R.

Hence, in the present embodiment, the provisional measurement valueFRF_p_R is subjected to conversion processing in S104 so as to obtain afinal measurement value FRF_R of the treading force of the right leg ofthe user A. The conversion processing of S104 is carried out accordingto the table shown in FIG. 7. More specifically, if FRF_p_R is apredetermined first threshold value FRF1 or less, then the measurementvalue FRF_R is set to zero. This prevents a very small error componentattributable mainly to the tightening of the shoelace of the foot-wornassembly 15R from being obtained as the measurement value FRF_R. If theprovisional measurement value FRF_p_R is larger than the first thresholdvalue FRF1 but is a second threshold value FRF2 (>FRF1) or less, thenthe measurement value FRF_R is linearly increased as the value ofFRF_p_R increases. If FRF_p_R exceeds the second threshold value FRF2,then the value of FRF_R is retained at a predetermined upper limit value(the value of FRF_R obtained when FRF_p_R equals the second thresholdvalue FRF2). The reason for setting the upper limit value of FRF_R willbe discussed hereinafter.

The above describes the processing of the right treading forcemeasurement processing means 60R. The same processing applies to theleft treading force measurement processing means 60L.

The arithmetic processor 51 then carries out in sequence the processingof the knee angle measurement processing means 61R, 61L and theprocessing of the supporting force measurement processing means 62R,62L. These processing will be explained below with reference to FIG. 8and FIG. 9. FIG. 8 is a block diagram showing the flows of theprocessing of the knee angle measurement processing means 61R, 61L andthe processing of the supporting force measurement processing means 62R,62L. The knee angle measurement processing means 61R and 61L share thesame processing algorithm, and the supporting force measurementprocessing means 62R and 62L also share the same processing algorithm.For this reason, any components related to the left knee anglemeasurement processing means 61L and the left supporting forcemeasurement processing means 62L are shown in parentheses in FIG. 8.

As representative processing, the processing of the right knee anglemeasurement processing means 61R and the right supporting forcecalculating means 62R will be explained. First, the right knee anglemeasurement processing means 61R carries out the processing in S201 andS202. Thus, a measurement value θ1_R of a knee angle of the right leglink 3R (the bending angle of the leg link 3R in the second joint 12R)is obtained. In S201, a provisional measurement value θ1 p_R of a kneeangle of the leg link 3R is calculated from an output of the rotaryencoder 28R.

Referring now to FIG. 9, in the present embodiment, an angle θ1_R formedby a segment S1 that connects the central point P related to the firstjoint 10R of the leg link 3R (the point P provides the rotational centerof longitudinal swing motions of the thigh frame 11R; the point P willbe hereinafter referred to as the longitudinal swing central point P)and the central point of the second joint 12R and a segment S2 thatconnects the central point of the second joint 12R and the central pointof the third joint 14R is measured as the knee angle of the right leglink 3R. The same applies to the knee angle of the left leg link 3L.FIG. 9 schematically shows the construction of the essential section ofthe leg link 3.

In this case, in S201 mentioned above, the rotational position of thesecond joint 12R in a state wherein the thigh frame 11R and the crusframe 13R of the leg link 3R hold a predetermined posture relationship(e.g., the posture state shown in FIG. 1), that is, in the state whereinthe knee angle θ1_R takes a predetermined value is defined as thereference. A rotational amount from the reference rotational position(the amount of a change in the rotational angle; this is proportional tothe rotational amount of the rotor of the electric motor 27R) ismeasured on the basis of an output signal of the rotary encoder 28R.Then, the value obtained by adding the measured rotational amount of thesecond joint 12R to the value of a knee angle of the leg link 3R at theaforesaid reference rotational position (this is stored and retained ina memory, which is not shown, beforehand) is determined as theprovisional measurement value θ1 p_R.

The provisional measurement value θ1 p_R sometimes contains ahigh-frequency noise component. Hence, the θ1 p_R is passed through alow-pass filter in S202 to obtain a final measurement value θ1 p_R of aknee angle of the leg link 3R.

The above describes the processing by the right knee angle measurementprocessing means 61R. The same processing applies to the left knee anglemeasurement processing means 61L.

Supplementally, in the present embodiment, the reason for measuring theangle θ1 formed by the segments S1 and S2 as the knee angle of the leglink 3 is because the measurement value of the angle θ1 is used mainlyfor the processing of the right/left desired share determining means 63,the details of which will be discussed hereinafter. In this case, in thewalking assisting device 1 according to the present embodiment, theangle formed by the axis of the thigh frame 11 of the leg link 3 and thesegment S1 is constant. Hence, in each knee angle measurement processingmeans 61, the angle formed by, for example, the axis of the thigh frame11 of the leg link 3 and the segment S2 related to the crus frame 13 maybe determined beforehand as the knee angle of the leg link 3. The angleθ1 may be determined from the knee angle by the processing by theright/left desired share determining means 63, which will be describedlater.

After the measurement value θ1_R of the knee angle of the leg link 3R isdetermined as described above, the processing of the right supportingforce measurement processing means 62R is carried out in S203. Morespecifically, a measurement value Fankle_R of a supporting force actingon the supporting force sensor 30R (that is, the total supporting forceshare of the leg link 3R) is calculated from the measurement value θ1_Rof the knee angle obtained in S202 and the detection values of thesupporting force sensor 30R (the detection values of the forces of twoaxes indicated by the voltage values of output signals of the supportingforce sensor 30R). This processing will be explained in detail withreference to FIG. 9.

The supporting force (the total supporting force share) Fankle_R actingon the supporting force sensor 30R of the leg link 3R is substantiallyequal to the translational force acting on the crus frame 13R from thethird joint 14R of the leg link 3R, as described above. Further, in thewalking assisting device 1 according to the present embodiment, thedirection of the translational force and the direction of Fankle_R areparallel to a segment S3 that connects the central point of the thirdjoint 14 of the leg link 3R and the central point P of the longitudinalswing.

Meanwhile, the supporting force sensor 30R detects a force Fz in az-axis direction perpendicular to the surface (the upper surface or thelower surface) of the supporting force sensor 30R and a force Fx in anx-axis direction, which is perpendicular to the z-axis and parallel tothe surface of the supporting force sensor 30R, as shown in the figure.The x-axis and the z-axis are coordinate axes fixed to the supportingforce sensor 30R, and are parallel to a plane that includes the arc ofthe guide rail 22. At this time, the detected Fz and Fx denote acomponent in the z-axis direction and a component in the x-axisdirection, respectively, of Fankle_R. Accordingly, as illustrated, ifthe angle formed by Fankle_R and the z-axis is denoted as θk, thenFankle_R can be calculated according to the following expression (1)from the detection values of Fz and Fx and θk.Fankle_(—) R=Fx·sin θk+Fz·cos θk  (1)

The angle θk is determined as follows. If the angle formed by thesegment S2 and the segment S3 (=the angle formed by the direction ofFankle and the segment S2) is denoted as θ2, then lengths L1 and L2 ofthe segments S1 and S2, respectively, in a triangle having the segmentsS1, S2 and S3 as its three sides take constant values (known values setin advance). Further, the angle θ1 formed by the segments S1 and S2 isthe measurement value θ1_R obtained as described above by the right kneeangle measurement processing means 61R. Therefore, the angle θ2 isdetermined by geometric calculation from the lengths L1 and L2 (thesevalues being stored and retained in a memory beforehand) of the segmentsS1 and S2, respectively, and the measurement value θ1_R of the angle θ1.

Specifically, in the triangle having the segments S1, S2 and S3 as itsthree sides, the relational expressions of (2) and (3) given below hold.L3 denotes the length of the segment S3.L3² =L1² +L2²−2·L1·L2·cos θ1  (2)L1² =L2² +L3²−2·L2·L3·cos θ2  (3)

Thus, L3 can be calculated according to expression (2) from the valuesof L1 and L2 and the measurement value of the angle θ1. Then, the angleθ2 can be calculated according to expression (3) from the calculatedvalue of L3 and the values of L1 and L2.

Further, if the angle formed by the z-axis and the segment S2 is denotedby θ3, then this angle θ3 takes a constant value set beforehand on thebasis of the angle at which the supporting force sensor 30 is mounted onthe crus frame 13. Then, the value of an angle θk required for thecalculation of expression (1) can be determined by subtracting the angleθ2 calculated as described above from the angle θ3 of the constant value(this value being stored and retained in a memory, which is not shown,beforehand).

Thus, in the processing of S203 of the right supporting forcemeasurement processing means 62R in the present embodiment, themeasurement value Fankle_R of the total lifting force share of the rightleg link 3R can be obtained according to the above expression (1) fromθk calculated as described above and the detection values Fx and Fz ofthe supporting force sensor 30 of the leg link 3R.

This completes the detailed explanation of the processing in S203 of theright supporting force measurement processing means 62R. The sameapplies to the processing of the left supporting force measurementprocessing means 62L.

In the present embodiment, the supporting force sensor 30 has used athree-axis force sensor or a two-axis force sensor to obtain themeasurement value Fankle of the total supporting force share of each leglink according to the above expression (1). However, even if thesupporting force sensor 30 is a one-axis force sensor, it is possible toobtain the measurement value Fankle. For example, if the supportingforce sensor 30 uses a sensor that detects only the force Fx in thex-axis direction shown in FIG. 9, then the measurement value Fankle canbe determined according to expression (4) given below. Further, if thesupporting force sensor 30 uses a sensor that detects only the force Fzin the z-axis direction shown in FIG. 9, then the measurement valueFankle can be determined according to expression (5) given below.Fankle=Fx/sin θk  (4)Fankle=Fz/cos θk  (5)

However, using expression (4) or (5) above leads to deterioratedaccuracy in the value of Fankle as the value of the angle θk approaches0 degree or 90 degrees. Therefore, it is desirable to use the aboveexpression (1) to obtain the measurement values of Fankle.

Alternatively, the measurement value Fankle may be obtained bydetermining the square root of the sum of a square value of Fx and asquare value of Fz. In this case, the measurement value θ1 of the kneeangle is unnecessary.

Supplementally, the processing by the measurement processing means 60,61, and 62 explained above does not necessarily have to be carried outin sequence. For instance, the processing of the measurement processingmeans 60, 61, and 62 may alternatively be carried out in parallel by atime-sharing manner or the like. If, however, θ1 is used in theprocessing by the supporting force measurement processing means 62R and62L, then the processing by the knee angle measurement processing means61R and 61L must be implemented before the processing by the supportingforce measurement processing means 62R and 62L.

In the present embodiment, the supporting force sensor 30 (the secondforce sensor) for measuring the total lifting force share of each leglink 3 is located between the third joint 14 and the crus frame 13 (theupper crus frame 13 a to be more accurate). Alternatively, however, thesupporting force sensor may be installed between the third joint 14 andthe foot-worn assembly 15 (e.g., between the third joint 14 and thejoining portion 34 of the foot-worn assembly 15). In this case, thesupporting force acting on the crus frame 13 from the third joint 14 canbe measured by measuring the rotational angle of the third joint 14 andcoordinate-converting the supporting force detected by the supportingforce sensor positioned between the third joint 14 and the foot-wornassembly 15.

Subsequently, the arithmetic processor 51 carries out the processing bythe right/left desired share determining means 63. This processing willbe explained in detail below with reference to FIG. 10. FIG. 10 is ablock diagram showing the flow of the processing by the right/leftdesired share determining means 63.

First, in S301, the measurement value Fankle_R of the total supportingforce share of the right leg link 3R and the measurement value Fankle_Lof the total supporting force share of the left leg link 3L determinedby the supporting force measurement processing means 62 as describedabove are added. This calculates a total supporting force Fankle_t. Thistotal supporting force Fankle_t corresponds to the measurement value ofthe total sum on both leg links 3 and 3, namely, the total sum of thesupporting forces acting on the supporting force sensors 30 or thetranslational forces acting on the crus frames 13 from the third joints14 of the leg links 3. The total supporting force Fankle_t issubstantially equal to the borne-by-the-assisting-device supportingforce.

Subsequently, an actual assist ratio, which is the ratio of the forceactually assisted by the walking assisting device 1 in a total treadingforce relative to the total treading force, is determined in S302 on thebasis of the result obtained by subtracting an assisting device weightsupporting force, which will be discussed later, from the above totalsupporting force Fankle_t, and the total sum of the measurement valuesFRF_R and FRF_L of the treading forces of the legs obtained by theaforesaid treading force measurement processing means 60, that is, themeasurement values (FRF_R+FRF_L) of the total treading force. To be morespecific, a supporting force required to support the weight calculatedby subtracting the total sum of the weights of portions below thesupporting force sensors from the total weight of the walking assistingdevice 1 (a supporting force that balances out the gravity correspondingto the weight) or a supporting force required to support the totalweight of the walking assisting device 1 (a supporting force thatbalances out the gravity corresponding to the total weight) is definedas the assisting device weight supporting force, and the magnitude ofthis assisting device weight supporting force is stored and retained ina memory, not shown, beforehand. Then, a value obtained by subtractingthe assisting device weight supporting force from the total supportingforce Fankle_t (this means an upward lifting force currently acting onthe user A from the seating part 2) is divided by the measurement valueof the total treading force (FRF_R+FRF_L) to determine the actual assistratio. In other words, the actual assist ratio is determined bycalculation expressed as: Actual assist ratio=(Fankle_t−Assisting deviceweight supporting force)/(FRF_R+FRF_L).

Subsequently, either the actual assist ratio or the set value of adesired assist ratio set by the assist ratio setting key switch 53 isselectively output in S303 according to a control signal of the liftingcontrol ON/OFF switch 54 (a signal indicating whether the switch 54 isON or OFF). In this case, according to the present embodiment, thelifting control ON/OFF switch 54 is turned on when the user A wishes toreceive a lifting force from the seating part 2. In other conditions,the lifting control ON/OFF switch 54 is set to OFF. In S303, if thelifting control ON/OFF switch 54 is OFF, then the actual assist ratiodetermined in the above S302 is selected and output. If the liftingcontrol ON/OFF switch 54 is ON, then the aforesaid set value of thedesired assist ratio is selected and output.

Subsequently, the output of S303 is passed through a low-pass filter inS304. Thus, a practical desired assist ratio as a desired assist ratioto be actually used is determined. The low-pass filter in S304 functionsto prevent a sudden change in the practical desired assist ratio when anoutput of S303 suddenly changes (e.g., when the set value of the desiredassist ratio is changed or when an output of S303 is switched from anactual assist ratio to the set value of the desired assist ratio). Thisis for eventually avoiding a sudden change in the lifting force actingon the user A from the seating part 2. The cutoff frequency of thelow-pass filter is, for example, 0.5 Hz.

Subsequently, in S305, the right desired lifting share, which is thedesired value of the share of the right leg link 3R, in the liftingforce applied to the user A from the seating part 2 is determined bymultiplying the aforesaid practical desired assist ratio by themeasurement value FRF_R of the treading force of right leg of the user Adetermined by the aforesaid right treading force measurement processingmeans 60R. Similarly, in S306, the left desired lifting share, which isthe desired value of the share of the left leg link 3L, in the liftingforce applied to the user A from the seating part 2 is determined bymultiplying the aforesaid practical desired assist ratio by themeasurement value FRF_L of the treading force of left leg of the user Adetermined by the aforesaid left treading force measurement processingmeans 60L.

The processing in S301 to S306 corresponds to the desired lifting sharedetermining means in the present invention.

Subsequently, in S307, a distribution ratio, which is a ratio fordistributing the aforesaid assisting device weight supporting force tothe right and left leg links 3, respectively, is determined on the basisof the magnitude of the measurement value FRF_R of a treading force ofthe right leg and the magnitude of the measurement value FRF_L of atreading force of the left leg that have been determined by the treadingforce measurement processing means 60 as described above. Thisdistribution ratio is composed of a right distribution ratio, which isthe ratio of allocation to the right leg link 3R, and a leftdistribution ratio, which is the ratio of allocation to the left leglink 3L, of an assisting device weight supporting force, the sum of thetwo distribution ratios being 1.

In this case, the right distribution ratio is determined to be the ratioof the magnitude of FRF_R relative to the sum of the magnitude of themeasurement value FRF_R and the magnitude of the measurement valueFRF_L, that is, FRF_R/(FRF_R+FRF_L). Similarly, the left distributionratio is determined to be the ratio of the magnitude of FRF_L relativeto the sum of the magnitude of the measurement value FRF_R and themagnitude of the measurement value FRF_L, that is, FRF_L/(FRF_R+FRF_L).In this case, in a state wherein one of the legs of the user A is astanding leg, while the other leg is a free leg (that is, in a one-legstanding state), the distribution ratio for the leg which becomes a freeleg is zero. Further, the distribution ratio for the leg which becomes astanding leg is 1.

The following will explain the reason for setting an upper limit valueof the measurement value FRF of a treading force of each leg in theconversion processing in S104 (see FIG. 6) of each of the aforesaidtreading force measurement processing means 60. In a state wherein bothlegs of the user A are standing (i.e., the state in a two-leg supportingperiod), the provisional measurement value FRF_p of a treading force ofeach leg usually tends to frequently fluctuate rather than smoothlychanges. In such a case, if the right and left distribution ratios weredetermined on the basis of the provisional measurement value FRF_p, thenthe distribution ratio would frequently change and the allocation ratioof each leg link 3 of a desired total supporting force would be apt tochange. As a result, a minute change would easily take place in alifting force acting on the user A from the seating part 2. This mayconsequently cause the user A to feel uncomfortable. For this reason,according to the present embodiment, an upper limit value of themeasurement value FRF of a treading force of each leg has been set toprevent a situation in which frequent changes take place in the rightand left distribution ratios in the state of a two-leg supportingperiod. In this case, in the state of a two-leg supporting period, boththe right and left distribution ratios will be basically maintained at1/2 except for a period immediately after the start and a periodimmediately before the end, thus stabilizing the right and leftdistribution ratios.

In FIG. 7 mentioned above, the measurement value FRF_R(L) may beobtained according to the table which has only the threshold value FRF1and in which the measurement value FRF_R(L) of a treading force linearlyincreases if the provisional measurement value FRF_p_R(L) of a treadingforce of each leg of the user A is the threshold value FRF1 or more. Thethreshold values FRF1, FRF2 and the like of the table for obtainingFRF_R(L) from the provisional measurement value FRF_p may beappropriately determined on the basis of the lifting force that feelscomfortable to the user A, the weight of the walking assisting device 1,the calculation capability of the control device 50, and the like.

Returning to the explanation of FIG. 10, subsequently, in S308, theright desired device supporting force share, which is the desired valueof the share of the right leg link 3R, in an assisting device weightsupporting force is determined by multiplying the aforesaid assistingdevice weight supporting force by the right distribution ratiodetermined in S307. Similarly, in S311, the left desired devicesupporting force share, which is the desired value of the share of theleft leg link 3L, in an assisting device weight supporting force isdetermined by multiplying the aforesaid assisting device weightsupporting force by the left distribution ratio determined in S307. Theprocessing in S307, S308, and S311 may be implemented in parallel to theprocessing of S301 to S306.

Subsequently, the processing in S309 and S310 related to the right leglink 3R and the processing in S312 and S313 related to the left leg link3L are carried out. According to the processing in S309 and S310 relatedto the right leg link 3R, first, in S309, the right desired devicesupporting force share obtained in S308 is added to the right desiredlifting share obtained in the aforesaid S305. Thus, a provisionalcontrol desired value Tp_Fankle_R as the provisional value of theaforesaid control desired value of the right leg link 3R is determined.Then, the provisional desired value Tp_Fankle_R is passed through alow-pass filter in S310 so as to determine the final control desiredvalue T_Fankle_R of the right leg link 3R. The low-pass filter in S309functions to remove noise components caused by a change in the kneeangle θ1 or the like. The cutoff frequency of the low-pass filter is,for example, 15 Hz.

Similarly, according to the processing in S312 and S313 related to theleft leg link 3L, first, in S312, the left desired device supportingforce share obtained in S311 is added to the left desired lifting shareobtained in the aforesaid S306. Thus, a provisional control desiredvalue Tp_Fankle_L as the provisional value of the aforesaid controldesired value of the left leg link 3L is determined. Then, theprovisional desired value Tp_Fankle_L is passed through a low-passfilter in S313 so as to determine the final control desired valueT_Fankle_L of the left leg link 3L.

The control desired value of each of the leg links 3 determined asdescribed above means the desired value of the share of each of the leglinks 3 in the total sum of the aforesaid assisting device weightsupporting force and the total lifting force applied to the user A fromthe seating part 2 (i.e., the aforesaid total supporting force).

The above is the processing by the right/left desired share determiningmeans 63. Supplementally, the processing for calculating the right andleft desired lifting shares in S305 and S306 is equivalent todistributing the result obtained by multiplying the total sum of themeasurement values FRF_R and FRF_L of the treading forces of the rightand left legs of the user A by the aforesaid practical desired assistratio (this corresponds to the desired value of the total lifting forceapplied to the user A from the seating part 2) to the right and left leglinks 3 on the basis of the aforesaid right distribution ratio and leftdistribution ratio.

The processing in S307, S308, and S311 corresponds to the distributingmeans in the present invention. Further, the processing in S309, S310,S312, and S313 corresponds to the means for determining a desired valueof a force-to-be-controlled in the present invention.

After carrying out the processing by the right/left desired sharedetermining means 63 as described above, the arithmetic processor 51implements the processing of the feedback manipulated variabledetermining means 64R, 64L and the feedforward manipulated variabledetermining means 65R, 65L in sequence or in parallel.

The processing of the feedback manipulated variable determining means64R, 64L will be explained with reference to FIG. 11. FIG. 11 is a blockdiagram showing the flows of the processing of the feedback manipulatedvariable determining means 64R, 64L. The feedback manipulated variabledetermining means 64R, 64L share the same algorithm, so that anycomponents related to the left feedback manipulated variable determiningmeans 64L are shown in parentheses in FIG. 11.

The processing of the right feedback manipulated variable determiningmeans 64R will be representatively explained. First, a differencebetween a control desired value T_Fankle_R of the right leg link 3Rdetermined by the right/left desired share determining means 63 and ameasurement value Fankle_R of the total supporting force share of theright leg link 3R measured by the right supporting force measurementprocessing means 62 (T_Fankle_R−Fankle_R) is calculated in S401. Then,the difference is multiplied by gains Kp and Kd in S402 and S403,respectively. Further, the calculation result of S403 is differentiatedin S404 (“s” in the figure denoting a differential operator), and thedifferential value and the calculation result of S402 are added in S405.Thus, a manipulated variable Ifb_R of the current of the right electricmotor 27 is calculated according to the PD control law, which serves asthe feedback control law, such that a manipulated variable Ifb_R of thecurrent of the right electric motor 27 converges the difference(T_Fankle_R−Fankle_R) to zero. The manipulated variable Ifb_R means afeedback component of an instructed current value of the right electricmotor 27.

In this case, according to the present embodiment, the values of thegains Kp and Kd are variably set on the basis of the measurement valueθ1_R of a knee angle of the leg link 3R. This is because the sensitivityof the electric motor 27R to changes in the lifting force of the seatingpart 2 in response to changes in current (changes in torque) of theelectric motor 27R varies according to the knee angle of the leg link3R. In this case, as the knee angle θ1_R increases (as the leg link 3Rstretches), the sensitivity of the electric motor 27R to the changes inthe lifting force of the seating part 2 in response to changes incurrent (changes in torque) increases. Hence, in S406, the values of thegains Kp and Kd are basically set such that the values of the gains Kpand Kd are reduced as the measurement value θ1_R of the knee angle ofthe leg link 3R increases according to a data table, which is not shown.

The above explains the processing of the right feedback manipulatedvariable determining means 64R. The same applies to the processing ofthe left feedback manipulated variable determining means 64L. In thepresent embodiment, the PD control law is used as the feedback controllaw so as to permit quick and stable control of lifting forces.Alternatively, however, a feedback control law other than the PD controllaw may be used.

Referring now to FIG. 12, the processing by the feedforward manipulatedvariable determining means 65R and 65L will be explained. FIG. 12 is ablock diagram showing the flows of the processing of the feedforwardmanipulated variable determining means 65R and 65L. The feedforwardmanipulated variable determining means 65R and 65L share the samealgorithm, so that any components related to the left feedforwardmanipulated variable determining means 65L are shown in parentheses inFIG. 12.

The processing of the right feedforward manipulated variable determiningmeans 65R will be representatively explained. In S501, the measurementvalue θ1_R of the knee angle of the leg link 3R measured by the kneeangle measurement processing means 61R is differentiated to calculate anangular velocity ω1_R of a bending angle of the second joint 12 of theleg link 3R. Further, in S502, the measurement value θ1_R of the kneeangle of the leg link 3R and the measurement value Fankle_R of the totalsupporting force share of the leg link 3R measured by the supportingforce measurement processing means 62R are used to calculate an actualtension T1, which is an actual tension of the wires 32 a and 32 b of theleg link 3R. The processing for calculating the actual tension T1 willbe explained with reference to FIG. 13. In FIG. 13, the leg links 3 areschematically shown. Further, in FIG. 13, like elements as those in FIG.9 are assigned like reference numerals.

First, a component Fankle_a that is orthogonal to the segment S2 of themeasurement value Fankle_R of a total supporting force share of the leglink 3R is calculated according to the following expression (7).Fankle_(—) a=Fankle_(—) R·sin θ2  (7)

The angle θ2 is an angle formed by Fankle_R and the segment S2, and theθ2 is calculated by geometric calculation using the measurement valueθ1_R, as explained above with reference to FIG. 9 (refer to expressions(2) and (3) given above).

Then, the Fankle_a determined as described above is multiplied by alength L2 of the segment S2, as shown in the following expression (8).Thus, based on Fankle_R, a moment M1 generated in the second joint 12(knee joint) is calculated.M1=Fankle_(—) a·L2  (8)

The moment generated in the pulley 31 by the actual tension T1 of thewires 32 a and 32 b balances out the moment M1 in a steady state.Further, the moment M1 is divided by an effective radius r of the pulley31 according to the following expression (9) so as to calculate theactual tension T1 of the wires 32 a and 32 b.T1=M1/r  (9)

The above is the detailed explanation of the processing in S502.

Returning to the explanation of FIG. 12, further, a desired tension T2of the wires 32 a and 32 b of the leg link 3R is calculated in S503. Thedesired tension T2 is a tension to be produced in the wires 32 a and 32b on the basis of a control desired value (the desired value of a totalsupporting force share) of the leg link 3R determined in the processingby the right/left desired share determining means 63. The desiredtension T2 is calculated in the same manner as in the calculationprocessing in S502. More specifically, a component orthogonal to thesegment S2 of the control desired value T_Fankle_R (refer to FIG. 13) iscalculated according to an expression in which Fankle_R in the rightside of the above expression (7) has been replaced by the controldesired value T_Fankle_R of the leg link 3R determined in the processingby the right/left desired share determining means 63. Then, thecalculated component is used to replace Fankle_a in the right side ofthe above expression (8) so as to calculate a desired moment of thesecond joint 12 of the leg link 3R. Further, the desired moment is usedto replace M1 in the right side of the above expression (9) to obtainthe desired tension T2 of the wires 32 a and 32 b.

The above explains the processing in S503.

After the processing in S501 to S503 is carried out, a manipulatedvariable of current of the electric motor 27R Iff_R is determined inS504 by predetermined feedforward processing by using the angularvelocity ω1_R of the second joint 12, the actual tension T1 of the wires32 a and 32 b, and the desired tension T2 calculated as described above.The manipulated variable Iff_R means a feedforward component of aninstructed current value of the electric motor 27R.

In the processing of S504, the manipulated variable Iff_R is calculatedaccording to a model expression represented by the following expression(10).Iff _(—) R=B1·T2+B2·ω1_(—) R+B3·sgn(ω1_(—) R)  (10)

where B2=b0+b1·T1, B3=d0+d1·T1

In expression (10), B1 denotes the coefficient of a constant, and B2 andB3 denote the coefficients represented by linear functions of the actualtension T1, as indicated by the note on expression (10). Further, b0,b1, d0, and d1 denote constants, and sgn( ) denotes a sign function.

This expression (10) is a model expression representing the relationshipamong the current of the electric motor 27, the tension of the wires 32a and 32 b, and the angular velocity ω1 of the second joint 12. A firstterm of the right side of expression (10) means the proportional term oftension, a second term means the term based on the viscous frictionalforce between the wires 32 a, 32 b and the pulley 31, and a third termmeans a term based on a dynamic frictional force between the wires 32 a,32 b and the pulley 31. A term based on angular acceleration of thesecond joint 12 (i.e., a term based on an inertial force) may be furtheradded to the right side of expression (10).

Supplementally, the constants B1, b0, b1, d0, and d1 used for thecalculation of expression (10) are experimentally identified by anidentification algorithm that minimizes the square value of thedifference between a value of the left side and a value of the rightside of expression (10) beforehand. Then, the identified constants B1,b0, b1, d0, and d1 are stored and retained in a memory, not shown, andused when the walking assisting device 1 is operated.

This completes the explanation of the processing of the rightfeedforward manipulated variable determining means 65R. The same appliesto the processing of the left feedforward manipulated variabledetermining means 65L.

Referring to FIG. 5, after calculating the manipulated variables Ifb_Rand Iff_R of the current of the electric motor 27R and the manipulatedvariables Ifb_L and Iff_L of the current of the electric motor 27L asdescribed above, the arithmetic processor 51 adds the manipulatedvariables Ifb_R and Iff_R by the addition processing means 66R. Thus,the instructed current value of the electric motor 27R is determined.Further, the arithmetic processor 51 adds the manipulated variablesIfb_L and Iff_L by the addition processing means 66L. Thus, theinstructed current value of the electric motor 27L is determined. Then,the arithmetic processor 51 outputs these instructed current values tothe driver circuits 52 associated with the individual electric motors27. At this time, the driver circuit 52 energizes the electric motors 27on the basis of the supplied instructed current values.

The control processing of the arithmetic processor 51 explained above iscarried out at predetermined control cycles. Thus, the torque to begenerated in the electric motors 27 and eventually the driving force ofthe second joint 12 (the knee joint) of the leg link 3 are controlledsuch that the measurement value Fankle of an actual total supportingforce share of each leg link 3 agrees with (converges to) the controldesired value T_Fankle corresponding to the leg link 3.

In the embodiment explained above, the desired value of a total desiredlifting force to be applied to the user A from the seating part 2 isdistributed to the left and right leg links 3L and 3R on the basis ofthe ratio of the treading force of the right leg and the treading forceof the left leg of the user A, and the assisting device weightsupporting force for supporting the total weight of the walkingassisting device 1 is distributed to the left and right leg links 3L and3R on the basis of the ratio of the treading force of the right leg andthe treading force of the left leg of the user A. Then, the controldesired value, which is the desired value of the total supporting forceshare of the leg links 3 is determined, and the supporting force of thecontrol desired value is generated in the leg links 3. Therefore,especially in a state wherein the lifting control ON/OFF switch 54 isON, a lifting force corresponding to an assist ratio set using the keyswitch 53 can be applied smoothly and stably to the user A from theseating part 2, thus making it possible to effectively reduce a load onthe legs of the user A.

Further, in a state wherein the lifting control ON/OFF switch 54 is OFF,the aforesaid actual assist ratio is determined as a practical desiredassist ratio. Thus, in this state, a load from the user A onto theseating part 2 always balances out a lifting force applied from theseating part 2 to the user A. In the balanced state, a vertical positionof the seating part 2 can be retained. In this state, when the liftingcontrol ON/OFF switch 54 is turned ON, a lifting force can be smoothlyapplied to the user A, obviating a situation wherein a sudden liftingforce is applied to the user A from the seating part 2.

Moreover, the current instructed values of the electric motors 27 aredetermined according to the PD control law (the feedback control law)and the feedforward control law in combination, thus permitting promptand stable lifting force control.

In the embodiment described above, the first force sensors have beencomposed of the MP sensor 38 and the heel sensor 39, these sensors 38and 39 being provided in the foot-worn assemblies 15 such that they arelocated between the sole of the foot of a standing leg of the user A anda floor, as shown in aforesaid FIG. 3. However, the mounting position ofthe first force sensor is not limited thereto. The first force sensormay alternatively be provided in the foot-worn assembly as shown in, forexample, FIG. 14. This case will be explained below as a secondembodiment.

Referring to FIG. 14, in the second embodiment, a foot supporting member100 is provided inside the annular member 36 of a foot-worn assembly 15.The foot supporting member 100 shaped like a slipper is composed of aplate-like foot sole member 101 (a member like a sole insert of a shoe),which comes in contact with substantially the entire bottom surface of afoot of a user A, and an arched member 102 (a member having anapproximately semicircular arc-shaped section) connected to the footsole member 101. The arched member 102 has its both lower ends connectedintegrally with both sides of the foot sole member 101. The toe portionof a foot of the user A can be inserted in the arched member 102. Withthe toe portion inserted therein, the foot is supported on the foot solemember 101. These foot sole member 101 and the arched member 102 areformed of a material, such as a metal or resin, having a predeterminedrigidity.

Further, a tensile strength sensor 103 constituting a first force sensoris provided between the outer surface of the top of the arched member102 and the inner surface of the top of the annular member 36. Thetensile strength sensor 103 is connected to the arched member 102 andthe annular member 36. The tensile strength sensor 103 is formed of, forexample, a tensile load cell. In this case, the foot supporting member100 is disposed inside the annular member 36 such that it is in contactwith neither the annular member 36 nor a shoe 35. With this arrangement,the foot supporting member 100 is suspended in the annular member 36through the intermediary of the tensile strength sensor 103 so that aforce for supporting the foot supporting member 100 from under acts fromneither the annular member 36 nor the shoe 35.

A cushion member for protecting a foot of the user A may be provided onthe upper surface of the foot sole member 101 or the inner surface ofthe arched member 102.

This completes the explanation of the construction of the foot-wornassembly 15 in the present embodiment. The foot-worn assembly 15 in thepresent embodiment is not equipped with the MP sensor 38, the heelsensor 39, and the sole insert 37. To attach the foot-worn assembly 15of the present embodiment to each foot of the user A, the toe portion ofthe foot is inserted in the arched member 102 of the foot supportingmember 100, and the foot is inserted into the shoe 35 through the topopening of the shoe 35, placing the foot on the foot sole member 101.

In the walking assisting device according to the present embodiment thathas the foot-worn assembly 15 constructed as described above, thetreading force of a leg of the user A that becomes a standing leg willbe detected by the tensile strength sensor 103 as a tensile strengthacting on the tensile strength sensor 103.

Further, in the present embodiment, outputs of the tensile strengthsensors 103 of the right and left foot-worn assemblies 15 instead ofoutputs of the MP sensor 38 and the heel sensor 39 are supplied totreading force measurement processing means 60 of an arithmeticprocessor 51. Each of the treading force measurement processing means 60obtains a force detection value, which is represented by an output ofthe tensile strength sensor 103 associated therewith (the tensilestrength taking a positive value) and which has been passed through alow-pass filter, as a provisional measurement value FRF_p of each leg ofthe user A. Further, each treading force measurement processing means 60determines the measurement value FRF of a treading force according tothe table shown in the aforesaid FIG. 7 from the provisional measurementvalue FRF_p.

The construction and processing other than those explained above are thesame as those of the aforesaid first embodiment.

The present embodiment is also capable of providing advantages similarto those of the first embodiment described above. In the presentembodiment, the tensile strength sensor 103 is provided between theuppermost portion of the inner peripheral surface of the annular member36 and the uppermost portion of the outer peripheral surface of thearched member 102. However, the position where the tensile strengthsensor 103 is disposed is not limited thereto; it may alternatively beinstalled on the upper, diagonal portion or on a side surface of thearched member 102 so that it is provided between the arched member 102and the annular member 36. Further alternatively, two or more tensilestrength sensors may be provided between the arched member 102 and theannular member 36, and the foot supporting member 100 may be suspendedin the annular member 36 through the intermediary of the plurality oftensile strength sensors. In this case, a treading force may be measuredon the basis of the total sum of the force detection values indicated byoutputs of the tensile strength sensors, as with the first embodiment inwhich a treading force has been measured on the basis of the total sumof the force detection values of the MP sensor 38 and the heel sensor39.

INDUSTRIAL APPLICABILITY

As described above, the present invention is useful as the one capableof properly assisting a user with his/her walking.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view (a view observed in a sagittal plane) of a walkingassisting device to which a first embodiment of the present inventionhas been applied.

FIG. 2 is a sagittal view taken at II in FIG. 1.

FIG. 3 is a sectional view taken at III-III in FIG. 1.

FIG. 4 is a block diagram schematically showing the construction(hardware construction) of a control device of the walking assistingdevice in FIG. 1.

FIG. 5 is a block diagram showing the functional construction of anarithmetic processor 51 provided in the control device in FIG. 4.

FIG. 6 is a block diagram showing the flows of the processing oftreading force measurement processing means 60R and 60L.

FIG. 7 is a graph showing a table used for the processing in S104 ofFIG. 6;

FIG. 8 is a block diagram showing the flows of the processing of kneeangle measurement processing means 61R and 61L and the processing ofsupporting force measurement processing means 62R and 62L.

FIG. 9 is a diagram for explaining the processing in S201 and S203 ofFIG. 8.

FIG. 10 is a block diagram showing the flow of the processing of aright/left desired share determining means 63.

FIG. 11 is a block diagram showing the flows of the processing offeedback manipulated variable determining means 64R and 64L.

FIG. 12 is a block diagram showing the flows of the processing offeedforward manipulated variable determining means 65R and 65L.

FIG. 13 is a diagram for explaining the processing of S502 of FIG. 12.

FIG. 14 is a diagram showing the construction of a foot-worn assembly ina second embodiment of the present invention.

1. A control device of a walking assisting device, wherein the walkingassisting device has a left and right side and is provided with aseating part that receives from above a part of a weight of a usersitting thereon, a pair of right and left thigh frames joinedrespectively to the seating part through an intermediary of firstjoints, a pair of right and left crus frames joined respectively to thethigh frames through an intermediary of second joints, a pair of rightand left foot-worn assemblies that are respectively joined to the crusframes through an intermediary of third joints and respectivelyconfigured for attaching to the feet of a right and left leg of the userand for coming into contact with the ground when the legs of the userbecome standing legs, an actuator for the left side of the device fordriving the second joint among the joints of a left leg link composed ofthe first joint, the thigh frame, the second joint, the crus frame, thethird joint, and the foot-worn assembly on the left side, and anactuator for the right side of the device for driving a second jointamong joints of a right leg link composed of the first joint, the thighframe, the second joint, the crus frame, the third joint, and thefoot-worn assembly on the right side, wherein the control devicecomprises: a treading force measuring element adapted to calculate atreading force of each leg of the user based on a force detection valueindicated by an output of a first force sensor provided in each of thefoot-worn assemblies; a second force sensor provided between a bottomend of the crus frame and the third joint of each leg link or betweenthe third joint and the foot-worn assembly of each leg link; aforce-to-be-controlled actual value measuring element adapted tocalculate, as an actual value of a force-to-be-controlled, a forceactually transmitted from the floor to the crus frame of each leg linkbased on a force detection value indicated by an output of the secondforce sensor; a desired assist ratio setting means for setting a desiredassist ratio, which is a desired value of a ratio of a force to besupplied by the walking assisting device in a total treading force,which is a total sum of the treading forces of the legs of the user,relative to the total treading force; a desired lifting sharedetermining means for determining a desired lifting share which is adesired value of a share of the left leg link and a desired liftingshare which is the desired value of a share of the right leg link in anupward lifting force to be applied to the user from the seating part bymultiplying the treading force of each leg of the user, which has beenmeasured by the treading force measuring element, by the desired assistratio; a distributing element adapted to calculate a distribution of asupporting force required to support, on the floor, a weight obtained bysubtracting a total weight of the portions below the second forcesensors of the walking assisting device from a total weight of thewalking assisting device, or a supporting force required to support thetotal weight of the walking assisting device on the floor to the leglinks on the basis of a ratio between the treading force of the left legand the treading force of the right leg of the user, which have beenmeasured by the treading force measuring means, thereby determining ashare of the left leg link and a share of the right leg link of thesupporting force as a desired device supporting force share of each leglink; a force-to-be-controlled desired value determining means fordetermining a desired value of the force-to-be-controlled of the leftleg link based on a total sum of a desired lifting share of the left leglink and a desired device supporting force share of the left leg linkand also for determining a desired value of the force-to-be-controlledof the right leg link based on a total sum of a desired lifting share ofthe right leg link and a desired device supporting force share of theright leg link; and an actuator controller adapted to control theactuator for the left side of the device on the basis of the actualvalue of the force-to-be-controlled of the left leg link and the desiredvalue of the force-to-be-controlled of the left leg link such that adifference between the actual value of the force-to-be-controlled andthe desired value of the left leg link approximates zero and forcontrolling the actuator for the right side of the device on the basisof the actual value of the force-to-be-controlled of the right leg linkand the desired value of the force-to-be-controlled of the right leglink such that a difference between the actual value of theforce-to-be-controlled and the desired value of the right leg linkapproximates zero.
 2. The control device of a walking assisting deviceaccording to claim 1, wherein the foot-worn assembly of each of the leglinks comprises an annular member for inserting a foot of the user, towhich the foot-worn assembly is to be attached, from a toe end thereof,and the foot-worn assembly is joined to the third joint of the leg linkthrough an intermediary of the annular member.
 3. The control device ofa walking assisting device according to claim 1, wherein the first forcesensor of each of the foot-worn assemblies comprises one or more forcesensors provided in each foot-worn assembly such that, when each leg ofthe user becomes the standing leg, the force sensors are positionedbetween at least either a location of a metatarsophalangeal joint or alocation of a heel of the foot on a bottom surface of the foot of thestanding leg and the floor, and the treading force measuring elementtakes a total sum of force detection values indicated by outputs of theforce sensors constituting the first force sensor of each foot-wornassembly as a force detection value of the first force sensor andcalculates the treading force of the leg of the user that has thefoot-worn assembly attached thereto on the basis of the force detectionvalue of the total sum.
 4. The control device of a walking assistingdevice according to claim 2, wherein a foot supporting member forsupporting the foot of the user is disposed in the annular member ofeach of the foot-worn assemblies such that it does not come in contactwith the annular member, and the foot supporting member is suspended inthe annular member through an intermediary of the first force sensor. 5.The control device of a walking assisting device according to claim 1,wherein if a force detection value of the first force sensor of each ofthe foot-worn assemblies is a predetermined first threshold value orless, then the treading force measuring element sets a calculated valueof the treading force of the foot attached to the foot-worn assembly tozero.
 6. The control device of a walking assisting device according toclaim 1, wherein if a force detection value of the first force sensor ofeach of the foot-worn assemblies is a predetermined second thresholdvalue or more, then the treading force measuring means obtains apredetermined upper limit value, which is set beforehand, as themeasurement value of a treading force of the foot attached to thefoot-worn assembly.
 7. The control device of a walking assisting deviceaccording to claim 1, comprising a selector switch for instructingwhether or not to carry out a lifting force control, wherein if anoperation state of the selector switch is an operation state instructingthat the lifting force control should be carried out, then the desiredlifting share determining means multiplies the treading force of eachleg of the user by the desired assist ratio to determine the desiredlifting share of the left leg link and the desired lifting share of theright leg link, or if an operation state of the selector switch is anoperation state instructing that the lifting force control should not becarried out, then the desired lifting share determining means determinesan actual assist ratio of a force actually supplied by the walkingassisting device in the total treading force of the user, the actualassist ratio indicating a ratio relative to the total treading force, byusing the actual value of the force-to-be-controlled of each leg linkcalculated by the force-to-be-controlled actual value measuring elementand the treading force of each leg of the user calculated by thetreading force measuring element, and then uses the determined actualassist ratio in place of the desired assist ratio to determine thedesired lifting share of the left leg link and the desired lifting shareof the right leg link.
 8. A control program on a processor forcontrolling a walking assisting device, wherein the walking assistingdevice has a left and right side and comprises a seating part thatreceives from above a part of a weight of a user sitting thereon, a pairof right and left thigh frames respectively joined to the seating partthrough an intermediary of first joints, a pair of right and left crusframes respectively joined to the thigh frames through an intermediaryof second joints, a pair of right and left foot-worn assemblies that arerespectively joined to the crus frames through an intermediary of thirdjoints, respectively configured for attaching to feet of a right andleft leg of the user and for coming into contact with the ground whenthe legs of the user become standing legs, an actuator for the left sideof the device for driving the second joint among joints of a left leglink composed of the first joint, the thigh frame, the second joint, thecrus frame, the third joint, and the foot-worn assembly on the leftside, an actuator for the right side of the device for driving a secondjoint among joints of a right leg link composed of the first joint, thethigh frame, the second joint, the crus frame, the third joint, and thefoot-worn assembly on the right side, a first force sensor provided ineach of the foot-worn assemblies for measuring a treading force of eachleg of the user, and a second force sensor installed between a lower endportion of the crus frame and the third joint of each leg link orbetween the third joint and the foot-worn assembly of each leg link, thecontrol program comprising the steps of: capturing an output of thefirst force sensor and determining a treading force to be actuallyapplied to the floor by the user from the foot of each leg of the userbased on a force detection value indicated by the output; capturing anoutput of the second force sensor and determining, as an actual value ofthe force-to-be-controlled, a force to be actually transmitted from thefloor to the crus frame of each leg link based on a force detectionvalue indicated by the output; capturing a set value of a desired assistratio, which is a desired value of a ratio of a force to be supplied bythe walking assisting device in a total treading force, which is a totalsum of the treading forces of the legs of the user, relative to a totaltreading force, and multiplying the determined treading force of eachleg of the user by the set value of the desired assist ratio so as todetermine a desired lifting share that is a desired value of a share ofthe left leg link and a desired lifting share that is a desired value ofa share of the right leg link in an upward lifting force to be appliedto the user from the seating part; determining the distribution of asupporting force required to support, on the floor, the weight obtainedby subtracting a total weight of portions below the second force sensorsof the walking assisting device from a total weight of the walkingassisting device or a supporting force required to support the totalweight of the walking assisting device on the floor to the leg linksbased on a ratio between the treading force of the left leg and thetreading force of the right leg of the user, which have been determined,thereby determining a share of the left leg link and a share of theright leg link out of the supporting force as the desired devicesupporting force shares of the respective leg links; determining adesired value of the force-to-be-controlled of the left leg link basedon a total sum of the desired lifting share of the left leg link and thedesired device supporting force share, which have been determined, andalso determining a desired value of the force-to-be-controlled of theright leg link based on a total sum of the desired lifting share of theright leg link and the desired device supporting force share, which havebeen determined; and generating a control output to control the actuatorfor the left side of the device on the basis of the actual value of theforce-to-be-controlled of the left leg link, which has been determined,and the desired value of the force-to-be-controlled of the left leglink, which has been determined, such that a difference between theactual value of the force-to-be-controlled and the desired value of theleft leg link approximates zero, and for generating a control output tocontrol an actuator for the right side of the device on the basis of theactual value of the force-to-be-controlled of the right leg link, whichhas been determined, and the desired value of the force-to-be-controlledof the right leg link, which has been determined, such that a differencebetween the actual value of the force-to-be-controlled and the desiredvalue of the right leg link approximates zero.
 9. The control program ofa walking assisting device according to claim 8, wherein the first forcesensor of each of the foot-worn assemblies comprises one or more forcesensors provided on each foot-worn assembly such that, when each leg ofthe user becomes the standing leg, the force sensors lie between atleast one of a location of a metatarsophalangeal joint and a location ofa heel of the foot on a bottom surface of the foot of the standing legand the floor, and the step of determining a treading force includestaking a total sum of the force detection values indicated by outputs ofthe force sensors constituting the first force sensor of each foot-wornassembly as the force detection value of the first force sensor, and fordetermining the treading force of the leg of the user, to which thefoot-worn assembly has been attached, on the basis of the forcedetection value of the total sum.
 10. The control program of a walkingassisting device according to claim 8, wherein the step of determiningtreading forces includes setting a value of the treading force of thefoot having the foot-worn assembly attached thereto to zero if the forcedetection value of the first force sensor of each of the foot-wornassemblies is a predetermined first threshold value or less.
 11. Thecontrol program of a walking assisting device according to claim 8,wherein the step of determining treading forces includes obtaining apredetermined upper limit value, which is set beforehand, as a value ofthe treading force of the foot having the foot-worn assembly attachedthereto if the force detection value of the first force sensor of eachof the foot-worn assemblies is a predetermined second threshold value ormore.
 12. The control program of a walking assisting device according toclaim 8, wherein a selector switch for instructing whether or not tocarry out lifting force control is provided in the walking assistingdevice, and the step of determining the desired lifting share of eachleg link includes multiplying the determined treading force of each legof the user by the set value of the desired assist ratio to determinethe desired lifting share of the left leg link and the desired liftingshare of the right leg link in an upward lifting force to be applied tothe user from the seating part if an operation state of the selectorswitch is an operation state giving instructions to carry out thelifting force control, or for determining an actual assist ratio of aforce actually being supplied by the walking assisting device out of thetotal treading force of the user, the actual assist ratio indicating aratio relative to the total treading force, by using the determinedactual value of the force-to-be-controlled of each leg link and thedetermined treading force of each leg of the user and then determiningthe desired lifting share of the left leg link and the desired liftingshare of the right leg link by using the determined actual assist ratioin place of the desired assist ratio if the operation state of theselector switch is an operation state giving instructions not to carryout the lifting force control.